Three trinuclear complexes constructed from a naphthalenediol-based bis(Salamo)-type tetraoxime ligand (H4L1), [Cu3(L1)(OAc)2]·CH3OH (1), [Zn3(L1)(OAc)2(CH3OH)2]·4CHCl3 (2), and [Cu2(L1)Na(NO3)(CH3OH)] (3), and one dinuclear complex, [{Cu(L2)}2] (4), based on an unexpected ligand H2L2 derived from the cleavage of H4L1 have been synthesized and characterized by X-ray diffraction analyses. Different anionic sources, transition metal salts, and rationally controlled reaction conditions play important roles in the construction of the resulting complexes with variable coordination geometries (coordination number ranges from 4 to 7), and four types of supramolecular network were controlled by noncovalent interactions, such as hydrogen bond, π···π stacking, C–H···π, Cu···π, and halogen-related interactions. The fluorescence properties of H4L1 and its complexes were investigated, and 2 exhibits unique bright cyan–yellow visible fluorescent emissions in different solvents.

Using 3-MeOsalamo H2L (H2L = 1,2-bis(3-methoxysalicylideneaminooxy)ethane) with Zn(OAc)2·2H2O, Ln(NO3)3·6H2O (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, and Tb), and 4,4′-bipy (4,4′-bipyridine) or H2bdc (terephthalic acid), three new families of heteromultinuclear ZnII–LnIII complexes: [{Zn(L)Ln(NO3)3(CH3OH)}2(4,4′-bipy)] (Ln = La (1·2CH3OH) and Ce (2)), [{Zn(L)Ln(NO3)3}2(4,4′-bipy)] (Ln = Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), and Tb(8)), [{(ZnL)2Ln}2(bdc)2]·(NO3)2·2CHCl3 (Ln = Ce (9), Pr (10) and Sm (11·2CH3CH2OH)), and 2∞[Zn(L)Ln(bdc)1.5] (Ln = Eu (12) and Gd (13·2CHCl3)) were obtained, respectively. Complexes 1–8 are heterotetranuclear dimers based on [Zn(L)Ln] moieties which are linked through the exo-dentate 4,4′-bipy having nitrogen-donor atoms. Heterohexanuclear complexes 9–11 constructed from almost linear trinuclear cationic [(ZnL)2Ln] moieties which are linked through the exo-dentate (bdc)2– bearing oxygen-donor atoms. Two 2D coordination polymers 12 and 13 are also assembled by [Zn(L)Ln] units with (bdc)2– linker. Furthermore, the luminescence properties of complexes 1–13 have been studied. An appropriate and selective linker could enhance the construction of a Salamo-type zinc(II)–lanthanide(III) complex possessing efficient luminescent properties.

Three heterometallic Ni(II)–M(II) (M = Ca, Sr and Ba) complexes, two discrete heterotrinuclear complexes [Ni2(L)Ca(OAc)2(CH3OH)2]·2C2H5OH·2CHCl3 (1) and [Ni2(L)Sr(OAc)2(CH3OH)2]·2CH3OH·2CH2Cl2 (2) and a discrete heterohexanuclear dimer [Ni2(L)Ba(OAc)2(CH3OH)2(H2O)]2·2CH3OH (3), were synthesized with a naphthalenediol-based acyclic bis(salamo)-type ligand (H4L), and characterized by elemental analyses, IR, UV-vis spectra, fluorescence spectra and X-ray crystallography. The heterometallic complexes were acquired by the reaction of H4L with 2 equiv. of Ni(OAc)2·4H2O and 1 equiv. of M(OAc)2 (M = Ca, Sr and Ba). The crystal structures of complexes 1–3 have been determined by single-crystal X-ray diffractions. Owing to the different nature of the N2O2 and O6 sites of the ligand H4L, the introduction of two different metal(II) atoms to the site-selective moiety, leads to the two Ni(II) atoms occupied both the N2O2 sites, an alkaline earth metal atom occupied the O6 site of the ligand (L)4− unit, respectively. Furthermore, the fluorescence properties have been discussed.

•H4L is a novel naphthalenediol-based bis(Salamo)-type tetraoxime compound.•H4L is a relay-sensor for high sensitive and selective detection of Zn2+/Pic−.•The H4L has two on/off switch fluorescence chains.•Both of the H4L and L-Zn2+ chemosensors have a certain practical application value and advantage.A novel naphthalenediol-based bis(Salamo)-type tetraoxime compound (H4L) was synthesized and characterized. Its Zn2+ complex was found to be highly sensitive for the detection of Pic− when dissolved in water-containing organic solvent. Sensor H4L acts as a relay-sensor for recognition of Zn2+ while the L-Zn2+ complex recognizes Pic− with high selectivity and sensitivity in acceptable physiological pH range. Moreover, The L-Zn2+ and its Pic− polymer complex display successive sensing of H+/OH− via increase (ON) and decrease (OFF) in fluorescence intensity. The crystal structure of the Zn2+ complex has been determined by single-crystal X-ray diffraction.Through complexation of naphthalenediol-based bis(Salamo)-type tetraoxime compound H4L with Zn(OAc)2·2H2O, a novel chemosensor ([Zn3(L)(μ-OAc)2(H2O)2]) for detection of Pic−, was obtained and characterized.Download high-res image (114KB)Download full-size image

•A novel Schiff base oxime ligand (H2L) can be used as a turn-on fluorescent sensor for selective detection of Zn2+.•Sensor H2L vividly discriminates between Zn2+ and Cd2+.•Two tetranuclear complexes, [Zn4(L)4] and [Ni4(L)4] were synthesized and their crystal structures have been characterized.•Sensor H2L is regular and consistent in its binding with transition metal ions with a good 4:4 stoichiometry.A novel Schiff-base oxime sensor H2L with the ONON chelating moieties was designed and synthesized based on condensation reaction. Different methods such as elemental analyses, FT-IR, 1H and 13C NMR were fully utilized in characterizing the structure of sensor H2L. The UV–vis spectra of the Zn2+ complex exhibit four clear isosbestic points which may be assigned to the ONON moieties binding to Zn2+. Sensor H2L operates on the CHEF and PET mechanisms, and the tendency of Zn2+ to strongly enhance fluorescence of sensor H2L was explored. Fluorescence measurements show that sensor H2L has excellent fluorescent selectivity for Zn2+ over many other metal ions based on intramolecular charge-transfer, and the results demonstrate that the binding between sensor H2L and Zn2+ is chemically reversible. The crystal structure of the Zn2+ complex has been characterized by X-ray crystallography.A novel Schiff base oxime sensor H2L operates on the CHEF and PET mechanisms. Fluorescence measurements show that sensor H2L has excellent fluorescent selectivity for Zn2+ over many other metal ions based on intramolecular charge-transfer. The crystal structure of the Zn2+ complex has been characterized by X-ray crystallography.

•Novel naphthalenediol-based acyclic bis(salamo)-type ligand was synthesized.•Spectral titrations clearly show the success of transformation from homotrinuclear to heterotrinuclear complexes.•The 3d–4f complexes have been synthesized and characterized structurally.•The different coordination modes of acetate ions in complexes 1, 2 and 3 have been observed.•Fluorescence properties of complexes 1, 2 and 3 have been discussed.Heterotrinuclear 3d–4f complexes with a naphthalenediol-based acyclic bis(salamo)-type ligand have been synthesized and structurally characterized. Spectral titrations clearly show that the heterotrinuclear complexes [Zn2(L)La(OAc)3] (1), [Zn2(L)Ce(OAc)3] (2) and [Zn2(L)Dy(OAc)3(CH3OH)]·CH2Cl2 (3) are acquired by the substitution reaction of the obtained homotrinuclear Zn(II) complex with 1 equiv. of Ln(NO3)3 (Ln3 + = La3 +, Ce3 + and Dy3 +). Two Zn(II) ions are penta- and hexa-coordinated with geometries of distorted tetragonal pyramid and octahedron. La(III) ion is deca-coordinated, adopting a distorted bicapped square antiprism geometry. Ce(III) ion is nona-coordinated with geometry of distorted capped square antiprism as well as Dy(III) ion. The different coordination modes of acetate ions in complexes 1, 2 and 3 lead to different coordination numbers of the lanthanide(III) ions. Furthermore, the structures and fluorescence properties have been discussed.Heterotrinuclear 3d–4f metal complexes with an naphthalenediol-based acyclic bis(salamo)-type ligand have been synthesized and structurally characterized. The coordination modes of three acetate ions are different in the complexes 1–3. Spectral titration clearly shows that the heterotrinuclear complexes [Zn2(L)La(OAc)3] (1), [Zn2(L)Ce(OAc)3] (2) and [Zn2(L)Dy(OAc)3(CH3OH)]·CH2Cl2 (3) were acquired by the substitution reaction of the reported homotrinuclear Zn(II) complex with 1 equiv. of Ln(NO3)3 (Ln3 + = La3 +, Ce3 + and Dy3 +).Download high-res image (125KB)Download full-size image

The homo/heterotrinuclear metal(II) complexes [Zn3(L)(OAc)2(CH3OH)2]·3CHCl3 (1), [Zn2(L)Ca(OAc)2]·CHCl3 (2), [Zn2(L)Sr(OAc)2] (3) and [Zn2Ba(L)(OAc)2(CH3OH)]·CH3OH·CHCl3 (4), with a novel acyclic bis(salamo)-type tetraoxime ligand H4L, were synthesized and characterized by elemental analyses, IR, UV–vis and fluorescence spectra. UV–vis titrations clearly show that complexation of H4L with Zn(II) ions affords a stoichiometric ratio of 3:1 (M:L) in a cooperative fashion. Complexes 2, 3 and 4 can acquire by the substitution reactions of complex 1 with 1 equivalent of M(OAc)2 (M2+ = Ca2+, Sr2+ or Ba2+). The crystal structures of complexes 1–4 have been determined by single-crystal X-ray diffraction. The coordinating ability of the [Zn3(L)]2+ units may be utilized as a cation recognition phenomenon.Four homo- and hetero-trinuclear zinc(II) complexes 1–4 have been successfully prepared with the acyclic naphthalenediol-based bis(salamo)-type ligand H4L, and structurally characterized. The homo-trinuclear complex, giving a cavity surrounded by six oxygen atoms, is expected to have a high affinity toward metal cations since the donor atoms are arranged in a cyclic fashion and are negatively charged. Using a “substitution reaction”, hetero-trinuclear complexes could be prepared from the homo-trinuclear complex effectively.Download high-res image (64KB)Download full-size image

Four new 3d–4f heterobinuclear complexes [Zn(L)Sm(Py)(NO3)3] (1), [Zn(L)Eu(OAc)(NO3)2] (2), [Zn(L)Tb(Py)(NO3)3] (3) and [Zn(L)Dy(OAc)(NO3)2] (4); Py = pyridine; H2L = 6,6′-dimethoxy-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol) have been successfully prepared by the one-pot reaction of H2L with zinc(II) acetate, lanthanide(III) nitrate and a simple auxiliary ligand Py. Although the heterobinuclear complexes 1–4 are prepared in the same reaction condition, the auxiliary ligand Py doesn’t coordinate to the Zn(II) center of the complexes 2 and 4. Instead, the bridging µ-acetato ligand is present in the complexes 2 and 4. The coordination of the auxiliary ligand Py in the complexes 1 and 3 leads to the smaller distortion of square pyramidal coordination site of Zn(II), the higher coplanarity between the planes of ZnO(phenoxo)2 and LnO(phenoxo)2, and the longer Zn⋯Ln distance compared with the complexes 2 and 4. Moreover, the ligand (L)2− can selectively sensitize Sm(III) ion from among Sm(III), Eu(III), Tb(III) and Dy(III) ions, although these complexes would often exhibit f–f luminescence.Four new 3d–4f heterobimetallic complexes 1–4 have been successfully prepared by the one-pot method, and characterized structurally. Moreover, the ligand (L)2− can selectively sensitize Sm(III) ion from among Sm(III), Eu(III), Tb(III) and Dy(III) ions, although these complexes would often exhibit f–f luminescence.Download high-res image (97KB)Download full-size image

A highly sensitive and selective fluorescence sensor for the detection of Zn2+ and Cu2+ was derived from a Salamo-type bisoxime ligand. The developed sensor is capable of detecting Zn2+ and Cu2+ in aqueous media through fluorescence turn on and off, respectively. In addition, the complexes of Zn2+ and Cu2+ could successfully sense the presence of H+/OH− via increase (ON)/decrease (OFF) in fluorescence intensity. Single crystal structures of Cu2+, Ni2+ and Cd2+ complexes have been characterized using X-ray crystallography, respectively. The Cu2+ complex forms a dinuclear structure with both Cu2+ being five-coordinated with square pyramidal geometries; the Ni2+ and Cd2+ complexes are both tetranuclear structures where the Ni2+ and Cd2+ are almost six-coordinated with slightly distorted octahedral geometries. More specifically, one of the Cd2+ forms a novel six-coordinated triangular prism geometry which is rarely reported.Sensor H3L could be utilized to sense the presence and absence of Zn2+/Cu2+ with high sensitivity and selectivity via metal displacement. The responses of Zn2+ and Cu2+ to H+ and OH− are considered to be an additional advantage of this sensor. Crystal structures of Cu2+, Ni2+ and Cd2+ complexes have been reported.Download high-res image (132KB)Download full-size image

Homo- and heterotrinuclear Co(II) complexes with a new acyclic bis(Salamo)-type ligand H4L, which bears a C-shaped O6 site by the metallation of the N2O2 Salamo moieties, were synthesized. The homotrinuclear complex [Co3(L)(OAc)2(CH3OH)2]·2CHCl3 (1) was obtained by the reaction of H4L with 3 equivalents of Co(OAc)2·4H2O. The heterotrinuclear complexes [Co2(L)Ca(OAc)2] (2), [Co2(L)Sr(OAc)2] (3) and [Co2(L)Ba(OAc)2(H2O)]·2CH3CH2OH (4) were acquired by the reaction of H4L with 2 equivalents of Co(OAc)2·4H2O and 1 equivalent of M(OAc)2 (M = Ca(II), Sr(II) and Ba(II)). In the crystal structures, the three metal(II) atoms occupy both the N2O2 and O6 sites of the ligand (L)4− moiety. Owing to the different nature of the N2O2 and O6 sites of the ligand H4L, the introduction of two different metal(II) atoms to the site-selective moiety, when compared with complex 1, leads to the replacement of the central Co(II) atom by different alkaline earth metal(II) atoms, namely the Ca(II), Sr(II) and Ba(II) atoms for complexes 2, 3 and 4, respectively. Magnetic measurements were performed on complexes 1–4, where an intramolecular ferromagnetic interaction was found in complex 3 and intramolecular antiferromagnetic interactions were found in complexes 1, 2 and 4. The magnetic susceptibilities above 50 K obey the Curie–Weiss law and their constant values were determined for all the complexes.The homo- and heterotrinuclear Co(II) complexes [Co3(L)(OAc)2(CH3OH)2]·2CHCl3 (1), [Co2(L)Ca(OAc)2] (2), [Co2(L)Sr(OAc)2] (3) and [Co2(L)Ba(OAc)2(H2O)]·2CH3CH2OH (4), constructed from the naphthalenediol-based acyclic bis(Salamo)-type ligand H4L, show different crystal structures. Different intramolecular magnetic interactions are found in the homo/hetero-trinuclear complexes 1–4.Download high-res image (102KB)Download full-size image

Two homotrinuclear Co(II) complexes, [Co3(L)(OAc)2(CH3OH)2] 2CHCl3 (1) and [Co3(L)(OAc)2(H2O)2] (2) based on a naphthalenediol-based acyclic bis(Salamo)-type tetraoxime ligand were synthesized. 1 and 2 were influenced by the coordinated methanol and water molecules, respectively, and their X-ray crystal structures revealed that they have similar molecular structures. Two terminal Co(II) ions, located at the N2O2 coordination spheres of the Salamo moieties, are both in distorted trigonal-bipyramidal geometries, while the third Co(II) ion in the central O4 cavity shows an octahedral geometry with two solvent molecules placed in the apical sites. Different solvent molecules lead to different supramolecular structures. The catecholase activities of 1 and 2 were examined using 3,5-di-tert-butylcatechol (3,5-DTBC) in acetonitrile solution under completely aerobic conditions. The catalytic reaction follows Michaelis–Menten enzymatic reaction kinetics with turnover numbers (Kcat) of 14.72 h−1 and 26.39 h−1 for 1 and 2, respectively.

A series of hetero-trinuclear Zn(II) complexes, [Zn2Ca(L)(OAc)2]·CHCl3 (1), [Zn2Sr(L)(OAc)2] (2) and [Zn2Ba(L)(OAc)2] (3) with a bis(salamo)-type tetraoxime ligand H4L were synthesized and characterized by elemental analyses, IR, UV-vis spectra etc. Spectral titrations and X-ray crystallography clearly show that the stoichiometry of the heterotrinuclear complexes are all 1 : 2: 1 (ligand/Zn(II)/M(II)). The different natures of the N2O2 and O6 sites of the ligand H4L lead to the site-selective introduction of two different kinds of metal(II) atoms. All the Zn(II) atoms are penta-coordinated with distorted square pyramidal geometries. The coordination numbers of Ca(II), Sr(II) and Ba(II) atoms in the O6 environment are all 8, and they have slightly distorted square antiprism geometries. Furthermore, ion competitive experiments show that the coordinating capability in the central O6 site is in the order of Ca(II) > Sr(II) > Ba(II).

Four hetero-bimetallic [ZnIILnIII] complexes with the general formula [Zn(L)(OAc)Ln(NO3)2] (Ln = Sm, Eu, Tb and Dy) were synthesized by the Salamo-type ligand H2L (6,6′-diethoxy-2,2′-[1,2-ethylenedioxybis(nitrilomethylidyne)]diphenol) with Zn(OAc)2·2H2O and Ln(NO3)3·6H2O (Ln = Sm, Eu, Tb and Dy), respectively. X-ray crystal diffraction analyses revealed that all the Zn(II) atoms were penta-coordinated, adopting distorted square pyramidal geometries, and the Ln(III) atoms were nona-coordinated, forming distorted tricapped trigonal prism geometries. In addition, three-dimensional supramolecular structures were assembled through intermolecular hydrogen-bond interactions. In the [ZnIILnIII] complexes, only [Zn(L)(OAc)Sm(NO3)2] showed obvious orange-red light emission under UV light due to the characteristic f–f transitions of Sm3+ ions, which meant that the ligand H2L could transfer energy from its excited state to the lowest excited state of the Sm3+ ion effectively. A decrease in the χMT value illustrated weak antiferromagnetic interaction exciting in the [Zn(L)(OAc)Tb(NO3)2] and [Zn(L)(OAc)Dy(NO3)2] complexes.

Through the self-assembly of a Salamo-type ligand H2L (H2L = 1,2-bis(3-methoxysalicylideneaminooxy)ethane) with Ni(OAc)2·4H2O, Ln(NO3)3·6H2O (Ln(III) = La(III), Gd(III), Tb(III) and Dy(III)) and Py (Py = pyridine) or 4,4′-bipy (4,4′-bipy = 4,4′-bipyridine) or H2bdc (H2bdc = terephthalic acid), nine new Ni(II)–Ln(III) heterometallic complexes [Ni(L)La(OAc)(NO3)2(Py)(CH3OH)]·CH3OH (1), [Ni(L)Dy(OAc)(NO3)2(Py)] (2), 1∞[Ni(L)La(NO3)3(4,4′-bipy)(CH3OH)] (3), 1∞[Ni(L)Tb(NO3)3(4,4′-bipy)] (4), [Ni(L)Dy(OAc)(NO3)2(4,4′-bipy)] (5), [{Ni(L)Ln(NO3)2(DMF)(CH3OH)}2(bdc)] (Ln = La (6) and Gd (7)) and [{Ni(L)Ln(NO3)2(DMF)}2(bdc)] (Ln = Tb (8) and Dy (9)) were obtained, respectively. The acetato ligand bridges the Ni(II) and Ln(III) (Ln = La (1) and Dy (2)) atoms in a μ2 fashion and the Py coordinates to the apical position by a nitrogen atom in the heterobimetallic complexes 1 and 2. Complexes 3 and 4 are 1D coordination polymers constructed from heterobimetallic [Ni(L)Ln] (Ln = La (3) and Tb (4)) units which are connected by the exo-dentate ligand 4,4′-bipy bearing nitrogen-donor atoms, but complex 5 is a heterobimetallic Ni(II)–Dy(III) complex which is prepared under the same reaction conditions as complexes 3 and 4. Four heterotetranuclear dimers were constructed from heterobimetallic [Ni(L)Ln] (Ln = La (6), Gd (7)), Tb (8) and Dy (9) units which are connected by the exo-dentate H2bdc ligand with oxygen-donor atoms. Magnetic measurements were performed on the Gd(III), Tb(III) and Dy(III) complexes.

•The Salamo-type complex with a ligand/metal(II) ratio of 2:1 hasn’t been reported.•The heptanuclear complex also hasn’t been synthesized in the reported Salamo-type metal complexes.•The two structures are very seldom (novel) and interesting.Two novel mono- and heptanuclear Ni(II) complexes, [Ni(HL1)2(EtOH)2]·2EtOH (1) and [Ni7(L2)3(μ3-OMe)2(μ3-OH)6(MeOH)6] (2), have been synthesized by the reaction of Ni(II) acetate with H2L1 and H2L2, respectively. In the Ni(II) complex 1, the ligand H2L1 was partially deprotonated, only NO donor atoms of one salicylidene moiety of the (HL1)− unit coordinate to Ni(II) atom. While all the three H2L2 ligands in the Ni(II) complex 2 were completely deprotonated. The seven Ni(II) atoms are all hexa-coordinated, and have two coordination environments. The fluorescence properties of the ligands, the Ni(II) complexes 1 and 2 have been discussed.Two novel mono- and heptanuclear Ni(II) complexes [Ni(HL1)2(EtOH)2]·2EtOH (1) and [Ni7(L2)3(μ3-OMe)2(μ3-OH)6(MeOH)6] (2) have been synthesized by the reaction of Ni(II) acetate with H2L1 and H2L2, respectively.

•A new asymmetric Salamo-type ligand H2L has been synthesized firstly.•Four new solvent-induced Ni(II) complexes have been synthesized and characterized structurally.•The Ni(II) complex 4 could been synthesized by the Ni(II) complexes 1, 2 or 3 dissolved in DMF solvent.•Electrochemical property of the Ni(II) complex 1 has been studied.Four new solvent-induced Ni(II) complexes with chemical formulae {[NiL(MeOH)(μ-OAc)]2Ni}·2MeOH (1), {[NiL(EtOH)(μ-OAc)]2Ni} (2), {[NiL(i-PrOH)(μ-OAc)]2Ni} (3) and {[NiL(DMF)(μ-OAc)]2Ni}·2DMF·0.44H2O (4), where H2L = 5-methoxy-4′-chloro-2,2′-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol, have been synthesized and characterized by elemental analyses, 1H NMR, FT–IR, UV–Vis spectra and X-ray crystallography. X-ray crystallographic analyses of the Ni(II) complexes reveal that they crystallize in the triclinic system, space group P1¯, and consists of three Ni(II) ions, two deprotonated L2− units, two μ-acetato ligands and two coordinated solvent molecules. In each of the Ni(II) complexes, the Ni(II) ions are hexa-coordinated with a slightly distorted octahedral coordination geometries. Although the molecule structures of the Ni(II) complexes are similar each other, obtained in different solvents, the supramolecular structures are entirely different. The complexes 1 and 3 possess a self-assembled infinite 2D and 1D supramolecular structures via the intermolecular hydrogen bonds, respectively. But the Ni(II) complexes 2 and 4 are formed 0D structures by intramolecular hydrogen bonds. Cyclic voltammetry is used to characterize electrochemical property of the Ni(II) complex 1.Four new solvent-induced Ni(II) complexes have been synthesized and characterized. Because of the coordination with different solvents, complexes 1, 2, 3 and 4 present two kinds of synthetic route: all the four complexes could been synthesized by the reaction of the Salamo-type ligand with Ni(CH3COO)2·4H2O in different solvents. The complex 4 also could been synthesized by the Ni(II) complexes 1, 2 or 3 dissolved in DMF solvent.

•A single-armed Salamo-type bisoxime H3L has been designed and synthesized firstly.•H3L can be used as a relay–sensor for relay recognition of Zn2+ and Cu2+ with high selectivity and sensitivity.•The complexes behave successive sensing of H+/OH− through fluorescence intensity increasing (ON) and decreasing (OFF).•Two novel Zn2+ and Cu2+ dinuclear complexes have been synthesized and determined by X-ray crystallographic analysis.A novel single-armed Salamo-type bisoximes (H3L) has been designed and synthesized firstly. A new application of Salamo-type bisoximes in ion recognition is investigated in detail. H3L can act as a relay–sensor for ratiometric recognition of Zn2+/Cu2+ with high selectivity and sensitivity. The Zn2+ and Cu2+ complexes behave successive sensing of H+/OH− through fluorescence intensity increasing (ON) and decreasing (OFF). Meanwhile, the crystal structures of the Zn2+ and Cu2+ complexes based on H3L, [Zn(L)(μ-OAc)Zn] and [Cu(L)(μ-OAc)Cu], have been determined by X-ray crystallographic analyses, respectively.

Five heterometallic Co(II)–Ln(III) complexes, a discrete heterodinuclear complex [CoLLa(Py)(NO3)3(CH3OH)] (1) (Py = pyridine), a heterotetranuclear dimer [Co2L2La2(4,4′-bipy)(NO3)6(CH3OH)2] (2) (4,4′-bipy = 4,4′-bipyridine) and three discrete heterodinuclear complexes [CoLLn(OAc)(NO3)2(CH3OH)] (Ln = Gd (3), Tb (4), Dy (5)), were synthesized with a hexadentate bisoxime ligand 1,2-bis(3-methoxysalicylideneaminooxy)ethane (H2L), and characterized by single crystal X-ray diffraction. The complexes 1, 3, 4 and 5 are discrete heterodinuclear structures, but the assembly of two dinuclear units [CoLLa(NO3)3(CH3OH)] and one 4,4′-bipyridine results in a discrete heterotetranuclear dimer 2. The Co(II) and La(III) atoms in the complexes 1 and 2 are penta- and decacoordinated, while the Co(II) and Ln(III) (Ln = Gd, Tb and Dy) atoms in the complexes 3, 4 and 5 are hexa- and nonacoordinated, respectively. Magnetic measurements were performed on the complexes 3, 4 and 5, where an intramolecular ferromagnetic interaction is found in the complex 3.Five heterometallic 3d–4f Co(II)–Ln(III) complexes, [CoLLa(Py)(NO3)3(CH3OH)] (1), [Co2L2La2(4,4′-bipy)(NO3)6(CH3OH)2] (2) and [CoLLn(OAc)(NO3)2(CH3OH)] (Ln = Gd (3), Tb (4), Dy (5)), derived from a hexadentate bisoxime. Moreover, magnetic measurements were performed on the complexes 3, 4 and 5.

Mono, di and heptanuclear metal(II) complexes with chemical formulae [Cu(L1)] (1), [Co2(L2)2]·2CH3CN (2) and [Ni7(L3)3(μ3-OEt)2(μ3-OH)6(EtOH)6] (3) have been synthesized by variational tetradentate Salamo-type ligands based on 3,5-dichlorosalicylaldehyde, and characterized by elemental analyses, FT-IR, UV–Vis spectra and X-ray crystallography. The Cu(II) complex 1 is a mononuclear complex with tetracoordinate Cu(II) atom lies in the N2O2 coordination sphere. The Co(II) complex 2 is a dinuclear complex with a central Co2O2 bridged unit via CoO bonds to form a head-to-head dimer, the pentacoordinate Co(II) atoms (Co1 and Co2) have a distorted square pyramidal (τ1 = 0.454) and trigonal bipyramidal (τ2 = 0.538) geometries, respectively. Interestingly, the Ni(II) complex 3 is a novel heptanuclear complex with an unprecedented 3:7 ligand to metal stoichiometry. Furthermore, fluorescence properties of the Cu(II) and Ni(II) complexes have been studied.Mono, di and heptanuclear metal(II) complexes with chemical formulae [Cu(L1)] (1), [Co2(L2)2]·2CH3CN (2) and [Ni7(L3)3(μ3-OEt)2(μ3-OH)6(EtOH)6] (3), have been synthesized by variational tetradentate Salamo-type ligands based on 3,5-dichlorosalicylaldehyde, and characterized structurally.

•A new asymmetric Salamo-type bisoxime has been synthesized firstly.•A novel complex {[CoL(PrOH)]2Co(H2O)}·PrOH has been synthesized and characterized.•The Co(II) complex is different from the previously trinuclear Co(II) complexes.•The results are important in coordination chemistry and supramolecular chemistry.A novel trinuclear Co(II) complex, {[CoL(PrOH)]2Co(H2O)}·PrOH, has been synthesized with 6-ethoxy-6′-hydroxy-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol (H3L), and characterized by elemental analyses, FT-IR, UV–Vis, molar conductance and X-ray crystallographic analysis. Two n-propanol molecules and one water molecule coordinate to three Co(II) ions and four μ-phenoxo oxygen atoms from two [CoL(CH3CH2CH2OH)] units also coordinating to Co(II) ion. All the penta-coordinated Co(II) ions of the Co(II) complex have a slightly distorted trigonal bipyramidal coordinated polyhedron. Meanwhile, the μ-phenoxo bridges play important roles in assembling Co(II) ions and L3− units, which is different from the normal trinuclear Co(II) complexes with the Salamo-type ligands reported early.Graphical abstractA novel Co(II) complex {[CoL(PrOH)]2Co(H2O)}·PrOH has been synthesized and characterized structurally. The Co(II) complex is different from the normal trinuclear Co(II) complexes with the Salamo-type ligands reported early, and form an infinite two-dimensional supramolecular structure.

•A halogen-substituted Salen-type bisoxime has been synthesized firstly.•A new complex [ZnL(H2O)2]n has been synthesized and characterized structurally.•The complex forms a self-assembling infinite dual metal–water chain-like structure.•Some new results are very important to coordination and supramolecular chemistry.A new hexa-coordinated zinc(II) complex, namely [ZnL(H2O)2]n, with N2O2 coordination sphere (H2L = 4,4′-dibromo-6,6′-dichloro-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol) has been synthesized and structurally characterized by elemental analyses, IR, UV–vis spectra and TG-DTA analyses, etc. Crystallographic data are monoclinic, space group P21/c, a = 24.634(2) Å, b = 10.144(1) Å, c = 7.9351(6) Å, β = 91.371(2)°, V = 1982.4(3) Å3, Dc = 2.099 g/cm3, Z = 4. The zinc(II) complex exhibits a slightly distorted octahedral geometry with halogen-substituted Salen-type bisoxime forming the basal N2O2 coordination sphere and two oxygen atoms from two coordinated water molecules in the axial position. The hydrogen-bonding and π–π stacking interactions have stabilized the zinc(II) complex molecules to form a self-assembling infinite dual metal–water chain-like structure with the nearest Zn⋯Zn distance of 4.954(4) Å.A new hexa-coordinated zinc(II) complex, namely [ZnL(H2O)2]n, with N2O2 coordination sphere has been synthesized and structurally characterized structurally. The zinc(II) complex exhibits a slightly distorted octahedral geometry with halogen-substituted Salen-type bisoxime forming the basal N2O2 coordination sphere and two oxygen atoms from two coordinated water molecules in the axial position. The hydrogen-bonding and π–π stacking interactions have stabilized the zinc(II) complex molecules to form a self-assembling infinite dual metal–water chain-like structure with the nearest Zn⋯Zn distance of 4.954(4) Å.

•A new asymmetric Salamo-type bisoxime has been synthesized firstly.•A novel complex {[NiL(n-PrOH)(μ-OAc)]2Ni}·n-PrOH·H2O has been synthesized and characterized structurally.•The hydrogen-bonding interactions have stabilized the Ni(II) complex molecules to form an infinite 1D supramolecular chain-like structure.•New results are very important to modern coordination and supramolecular chemistry.A novel trinuclear Ni(II) complex [{NiL(n-PrOH)(μ-OAc)}2Ni]·n-PrOH·H2O with an asymmetric Salamo-type ligand, 5-methoxy-4′-bromo-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol (H2L), has been synthesized and characterized by elemental analyses, IR, UV/Vis and fluorescence spectra and molar conductance measurement. The crystal structure of the Ni(II) complex has been determined by single-crystal X-ray diffraction. Two acetate groups coordinating to three Ni(II) ions through NiOCONi bridges and four μ-phenoxo oxygen atoms from two [NiL(n-PrOH)] units also coordinating to Ni(II) ions. In the Ni(II) complex, two n-propanol molecules are coordinated to the two terminal Ni(II) ions having slightly distorted octahedral coordination geometries and form a trinuclear structure, There are also one non-coordinated n-propanol and one non-coordinated water molecule. In the crystal structure, the Ni(II) complex is linked by intermolecular hydrogen bonds into an infinite 1D supramolecular chain-like structure.Graphical abstractA supramolecular trinuclear Ni(II) complex {[NiL(n-PrOH)(μ-OAc)]2Ni}·n-PrOH·H2O with 5-methoxy-4′-bromo-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol (H2L), has been synthesized and characterized structurally. Two n-propanol molecules are coordinated to the two terminal Ni(II) ions which are linked by two acetate groups coordinated to the central Ni(II) ion forming NiOCONi bridges. Four μ-phenoxo oxygen atoms from two deprotonated L2− units also bridge the three Ni(II) ions, forming a trinuclear structure. There are also one non-coordinated n-propanol and one water molecule. In the crystal structure, the Ni(II) complex is linked by intermolecular hydrogen bonds into an infinite 1D supramolecular chain.

Two new Cu(II) complexes, [Cu(L1)2] (1) and [Cu(L2)2] (2) (HL1 = (E)-3-bromo-5-chloro-2-hydroxy benzaldehyde O-methyl oxime; HL2 = (E)-3-bromo-5-chloro-2-hydroxy benzaldehyde O-ethyl oxime), have been synthesized and characterized by physicochemical and spectroscopic methods. X-ray crystallographic analyses show that complexes 1 and 2 have similar structures, consisting of one Cu(II) atom and two L− units. In both complexes, the Cu(II) atom, lying on an inversion center, is four-coordinated in a trans-CuN2O2 square-planar geometry by two phenolate O and two oxime N atoms from two symmetry-related N,O-bidentate oxime ligands. Moreover, both complexes form an infinite three-dimensional supramolecular structure involving intermolecular C–H···Br hydrogen bonds and π···π stacking interactions between the metal chelate rings and aromatic rings. Substituent effects in the two complexes are discussed.

Two CoII complexes, namely {[CoL(MeOH)(μ-OAc)]2Co}·2MeCN·2MeOH (1) and {[CoL(EtOH)(μ-OAc)]2Co}·3EtOH (2) (H2L=3,3′-dimethoxy-2,2′-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol), have been synthesized and characterized by X-ray crystallography. Both complexes contain octahedral coordination geometries, comprising three CoII atoms, two deprotonated bisoxime L2− units in which four μ-phenoxo oxygen atoms form two [CoL(X)] (X = MeOH or EtOH) units, two acetate ligands coordinated to three CoII centers through Co–O–C–O–Co bridges, and coordinated and non-coordinated solvent. Both complexes exhibit 2D supramolecular networks through different intermolecular hydrogen-bonding interactions.

Two new mono- and dinuclear Cu(II) complexes, namely [CuL1]·0.5H2O (1) and [(Cu2(L2)2)(DMF)]·0.5DMF (2) (H2L1 = 1,2-bis{[(Z)-(3-methyl-5-oxo-1-phenyl-1H-pyrazolidin-4(4H)-yl)(phenyl)]methylene-aminooxy}ethane; H2L2 = 1,3-bis{[(Z)-(3-methyl-5-oxo-1-phenyl-1H-pyrazolidin-4(4H)-yl)(phenyl)] methyleneaminooxy}propane), have been synthesized and characterized by X-ray crystallography. The unit cell of complex 1 contains two crystallographically independent but chemically identical [CuL1] molecules and one crystalline water molecule, showing a slightly distorted square-planar coordination geometry and forming a wave-like pattern running along the a-axis via hydrogen bonding and π···π stacking interactions. Complex 2 has a dinuclear structure, comprising two Cu(II) atoms, two completely deprotonated phenolate bisoxime (L2)2− moieties (in the form of enol), and both coordinated and hemi-crystalline DMF molecules. Complex 2 has square-planar and square-pyramidal geometries around the two copper centers, whose basic coordination planes are almost perpendicular and form an infinite three-dimensional supramolecular network structure involving intermolecular C–H···N, C–H···O, and C–H···π(Ph) hydrogen bonding and π···π stacking interactions of neighboring pyrazole rings.

Mononuclear and trinuclear Cu(II) complexes with chemical formula [CuL]·CH3OH (1) and [{(Cu(μ-L))2(OAc)2}Cu] (2), where H2L = 2,2′-[1,1′-(ethylenedioxydinitrilo)diethylidyne]diphenol, have been synthesized and characterized by elemental analyses, 1H NMR, IR and UV–vis spectra et al. Crystallographic data of complex 1 reveal the formation of an asymmetric mononuclear structure and a slight distortion toward tetrahedral geometry from the square planar structure, in which the introduction of the non-coordinated methanol molecule lead to the assembly of the 1D chains by hydrogen bonding, Cu⋯π and π⋯π interactions. Complex 2 have the elongated square pyramidal geometries for the two terminal Cu(II) ions and an octahedral coordinated geometry for the central Cu(II) ion. In complex 2, two acetate ions coordinate to three Cu(II) ions adopting a familiar syn–syn (μM-O-C-O-M) coordinated fashion. The central Cu(II) ion sits in a crystallographic inversion centre. Therefore, the whole molecule of complex 2 is rigorously centrosymmetric, and forms a 3D supramolecular networks through intermolecular C–H⋯O and C–H⋯π interactions.

Three new supramolecular complexes, [Cu(HL1)] (1), [Cu(L2)H2O] (2) and [Co2(L2)2]·3CH3CN (3), were designed and synthesized by the reaction of 5-hydroxy-4′,6′-dibromo-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol (H3L1) with Cu(II) acetate hydrate (for 1); and 6-methoxy-4′,6′-dibromo-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol (H2L2) with Cu(II) acetate hydrate (for 2) and cobalt(II) acetate tetrahydrate (for 3), respectively, and were characterized by element analyses, X-ray crystallography, FT-IR, UV–Vis and fluorescence spectra. Complex 1 is mononuclear and tetra-coordinated and adopts a distorted square-planar geometry, likewise, complex 2 is mononuclear and penta-coordinated with a square-pyramidal geometry, however, complex 3 is dinuclear with the two Co(II) atoms having the same coordination environments and adopt a trigonal bipyramidal geometry. These self-assembling complexes form different dimensional supramolecular structures through inter- and intramolecular hydrogen bonds. Meanwhile, photophysical properties of the three complexes have also been discussed. Furthermore, the fluorescence behaviors of the two Cu(II) complexes in DMF are discussed.Three new supermolecular complexes, [Cu(HL1)] (1), [Cu(L2)H2O] (2) and [Co2(L2)2]·3CH3CN (3), have been synthesized and structurally characterized. These self-assembling complexes form different dimensional supramolecular structures through intermolecular and intramolecular hydrogen bonds. Meanwhile, the fluorescence behavior of the two Cu(II) complexes in DMF is discussed.