•Two transition-metal-based coordination polymers have been synthesized and characterized.•Compounds 1 and 2 exhibit both thermal stability and hydrolytic robustness.•Both compounds can serve as a highly sensitive luminescent sensors for aqueous detection of hydrogen sulfide.Two new coordination polymers of [Zn(L)(4,4′-bpy)0.5].(H2O)0.25(1) and [Cd4(L)4(4,4′-bpy)2].(H2O)(2) have been solvothermally synthesized from semi-rigid ligand H2L (H2L = 4,4′-dicarboxy-4″-nitrotriphenylamine) and auxiliary ligand 4,4′-bpy (4,4′-bpy = 4,4′-bipyridine), which have been fully characterized by single-crystal X-ray diffraction, PXRD, IR and elemental analysis. Compound 1 is composed of interdigitated 2-D square-grid layers which are assembled from 1-D beaded chain pillared by 4,4′-bpy, whereas compound 2 comprises two interpenetrated 3-D pcu nets which are constructed by 4,4′-bpy pillared 2-D square-grid layers. Compound 1–2 display both thermal stability and hydrolytic robustness. What is the most interesting finding is that both compounds exhibit strong luminescence in aqueous solution, and each of them can serve as a highly sensitive and selective fluorescence “turn-off” sensor for aqueous detection of hydrogen sulfide.Two new coordination polymers of 1 and 2 have been solvothermally synthesized and characterized. It is important to highlight that both compounds can serve as fluorescence sensors for aqueous detection of hydrogen sulfide.Download high-res image (91KB)Download full-size image

•Two unique isomorphic transition-metal-based coordination polymers have been synthesized and characterized.•Both compounds exhibit a 2-D square-grid layer and one-dimensional rhombus channel along the c axis.•Compound 1 can serve as a highly sensitive luminescent sensors for the detection of Fe3 + ion in DMAc solution.Two Zn2 + and Co2 +-based metal-organic frameworks, [Zn4(L)4(4,4′-bpy)(H2O)2] 2H2O 2CH3CN (1) and [Co4(L)4(4,4′-bpy)(H2O)2].2H2O (2), have been synthesized hydrothermally from mixed ligands of H2L (4,4′-dicarboxy-4″-nitrotriphenyl-amine) and 4,4′-bpy (4,4′-bipyridine). Single-crystal X-ray crystallography reveals that compounds 1 and 2 are isomorphic both featuring a 2-D square-grid layer assembled from one-dimensional cage-connected-cage chain and 4,4′-bpy pillar. Both compounds exhibits one-dimensional rhombus channel with the dimension of about 14.12 × 7.62 Å2 along the c axis. Compound 1 shows strong photoluminescence which has the capability of selective sensing of Fe3 + ion in DMAc.Two isomorphic coordination polymers of 1 and 2 have been synthesized hydrothermally and characterized. Both compounds exhibits one-dimensional rhombus channel with the dimension of about 14.12 × 7.62 Å2. In addition, compound 1 shows strong photoluminescence in DMAc which has the capability of selective sensing of Fe3 + ion.Download high-res image (332KB)Download full-size image

Two new coordination polymers, Cu(Hbsal)2(4,4′-bpy)2 (1) and Cu(bsal)(4,4′-bpy)·DMF (2), have been synthesized from 5-bromosalicylic acid (H2bsal) and the auxiliary ligand 4,4′-bipyridine (4,4′-bpy) through a slow diffusion method. Compound 1 is composed of parallel 1D linear chains, whereas compound 2 represents a non-interpenetrated 3D sod net which is constructed from left and right-handed helical chains alternately separated by 4,4′-bpy. The most interesting finding is that compound 1 can be irreversibly transformed into 2 in a crystal-to-crystal manner in the case that compound 1 is immersed in the DMF solvent. Particularly, the 1D-to-3D crystal-to-crystal structural transformation also incurs a drastic change in the magnetic properties of 1 and 2.

Three transition-metal-based coordination polymers (1: Co2+; 2: Ni2+ and 3: Cd2+) have been solvothermally synthesized from a newly designed polytopic ligand of 4-(carboxymethoxy)-[1,1′-biphenyl]-3,4′-dicarboxylic acid (H3Lws) that integrates both flexible aliphatic and rigid aromatic carboxylate groups. In 1, each H3Lws ligand connects two Co2+ ions in the partially deprotonated form of HLws2−, whereas the H3Lws ligands in 2 and 3 are fully deprotonated (Lws3−), each linking three Ni2+ ions and seven Cd2+ ions, respectively. Compound 1 shows a one-dimensional chain structure, and compound 2 is composed of a two-dimensional waved sheet based on Ni4(μ3-OH)2(μ2-O)4 cluster. Compound 3 has a three-dimensional network structure that is constructed of two-dimensional Cd/O-based layers pillared by Lws3− spacers. Compounds 1–3 exhibit both thermal stability (>340 °C) and hydrolytic robustness even under the heating condition. In particular, compound 3 displays the strongest luminescence in aqueous solution, which is almost 2.5-fold greater than that in organic solvents. More importantly, it is proved that compound 3 can serve as a highly sensitive luminescent sensor for aqueous detection of those nitro phenolic aromatics.Three transition-metal-based coordination polymers (1: Co2+; 2: Ni2+ and 3: Cd2+) have been solvothermally synthesized and characterized from a newly designed semi-rigid polytopic ligand of H3Lws. It is important to highlight that compound 3 can serve as a highly sensitive luminescent sensor for aqueous detection of those nitro phenolic aromatics.Download high-res image (167KB)Download full-size image

Solvothermal reactions of 2-ppds (2-ppds = di[4-(pyridin-2-yl)pyrimidinyl]disulfide) with ZnX2 (X = Cl, ClO4) in mixed CH3OH–CH2Cl2 solvent have been investigated. To better understand these reactions, solution analysis was conducted in parallel with single-crystal X-ray diffraction analysis of the in situ generated coordination complexes. At 120 °C, solvothermal reaction of 2-ppds with ZnCl2 resulted in a discrete mononuclear coordination complex formulated as [ZnCl2(L1)] (1), in which the zwitterion L1 (1-methyl-4-(pyridin-2-yl)pyrimidin-1-ium-2-olate) was formed in situ from 2-ppds, and solution analyses based on TLC and ESI–MS further showed that the reaction solution also contains in situ transformed products of L2 (bis(4-(pyridin-2-yl)pyrimidin-2-yl)sulfane) and L3 (2-methoxy-4-(pyridin-2-yl)pyrimidine). At 90 °C, solvothermal reaction between 2-ppds and Zn(ClO4)2 led to a discrete mononuclear coordination complex formulated as [Zn(SH)(L2)]ClO4 (2) that features a terminally bound –SH group, while the reaction solution was also found to contain a library of in situ reaction products of 2-ppds including L1, L2, L3 and L4 ((4-(pyridin-2-yl)pyrimidin-2-yl) 4-(pyridin-2-yl)pyrimidine-2-sulfonothioate). Thus, the heterocyclic disulfide 2-ppds is transformed in situ into various organic products in a series of reactions involving C–S/S–S bond cleavage.

Three Cd(II)-based coordination polymers 1–3 with unique structures and topologies have been successfully constructed under solvothermal conditions by use of a newly designed N-containing rigid triangular ligand tris(4-(4H-1,2,4-triazol-4-yl)phenyl)amine (TTPA-4), wherein the structural interpenetration can be modulated by aromatic dicarboxylate coligands including thiophene-2,5-dicarboxylic acid (TDA) and terephthalic acid (TPA). Without using coligands, a noninterpenetrating porous 3-D network of 1 with nia topology was obtained. With the aid of the V-shaped TDA coligand, a 4-fold interpenetrating 3-D network of 2 resulted that is built from (2,3,7)-connecting (42.6)(44.6.88.104.124)(4)2 net. In the presence of the linear TPA auxiliary ligand, an 8-fold interpenetrating 3-D network of 3 was produced that is assembled by 3-connecting uninodal srs net. Particularly, compound 1 displays interesting dual function as the result of its unique structural attributes, which not only shows superb sensitivity for nitroaromatics (NACs) with phenolic group but also impressive removal capabilities of toxic Cr2O72– oxoanion pollutant from aqueous solution.

An anionic zeolite-like metal–organic framework (AZMOF) with a twisted partially augmented the net, known as the “Moravia” net, [(CH3)2NH2]6[Sr13(O)3(BTTC)8(OH)2(H2O)16]·xS (Sr-BTTC, where S represents non-coordinated solvent molecules, and BTTC is the abbreviation of benzo-(1,2;3,4;5,6)-tris-(thiophene-2′-carboxylic acid)), has been solvothermally synthesized and characterized, which possesses an anionic framework and nano-sized sodalite cage. Through cation-exchange, Sr-BTTC is capable of uptaking large organic cationic dyes including Rhodamine B (RB), Basic Red 2 (BR2), Crystal Violet (CV) and Methylene Blue (MB), amongst which the adsorption capability for RB (up to 545 mg g−1), and BR2 (up to 675 mg g−1) is the highest for reported absorbants to date.

Under different solvothermal conditions, the reactions of 2-ppds (2-ppds = di[4-(pyridin-2-yl)pyrimidinyl]disulfide) with CuX2 (X = ClO4 or Cl) produced markedly different results because of diverse in situ reactions of 2-ppds involving dynamic S–S and C–S bond cleavage. At 90 °C, reaction of 2-ppds with Cu(ClO4)2 in CH3CN–CH2Cl2-mixed solvent yielded a discrete mononuclear complex, [Cu(L1)2(ClO4)]ClO4 (1), in which 2-ppds was converted into a zwitterion of L1 (L1 = 4-(pyridin-2-yl)pyrimidin-2-ol) involving C–S bond scission followed by attack of water. At 120 °C in DMF–MeOH solvent, reaction of 2-ppds with Cu(ClO4)2 resulted in transformation to L2 (L2 = 4-(pyridin-2-yl)pyrimidine-2-thiolate) through reductive cleavage of the S–S bond concurrent with reduction of Cu2+ to Cu+, leading to the formation of a single tetranuclear coordination complex, [Cu4(L2)4] (2), that comprises a unique Cu4S4 cluster. When the reaction between 2-ppds and CuCl2 was carried out at 90 °C in CH3CN–H2O solvent, a discrete coordination complex, [Cu(L3)(H2O)Cl]Cl (3), was obtained, resulting from conversion of 2-ppds into L3 (L3 = bis(4-(pyridin-2-yl)pyrimidin-2-yl)sulfane) through extrusion of one S atom from the S–S bond.

Two coordination polymers with the heterofunctional ligand 4-PPT (4-(pyridin-4-yl)pyrimidine-2-thiol), {[Ni(4-PPT)2]·2(DMF)}n (1) and {[Cu2(4-PPT)2]·2(DMF)}n (2), have been isolated by reaction with Ni(OAc)2 and CuBr2, respectively. 1 shows a two-dimensional (2-D) layered structure with a 4-connected sql topology wherein the 4-PPT ligand exhibits a uniform μ2-1, κS κN(pyrimidine): 2, κN(pyridine) bridging mode. 2 also features an sql net based on a unique CuI4S4 cluster in which the 4-PPT ligand adopts two kinds of coordination modes, viz. μ3-1, κN(pyrimidine): 2,3, κS and μ4-1, κN(pyrimidine): 2,3, κS: 4, κN(pyridine). For comparison, the reaction of CuBr2 with 3-PPT (4-(pyridin-3-yl)pyrimidine-2-thiol, an isomer of 4-PPT) under the same conditions was also examined, which yielded a 2-D Cu(I)-based coordination polymer with the 63-hcb topology, [CuBr(3-ppds)]n (3) (3-ppds = di(4-(pyridin-3-yl)pyrimidin-2-yl)disulfide). In 3,3-ppds was in situ generated from 3-PPTvia an S–S oxidative coupling reaction, concurrent with in situ reduction CuII–CuI. UV–Vis diffuse reflectance and luminescence spectra have been measured for 1 and 2 in order to compare their photophysical properties.Assembly of the 4-PPT ligand with Ni(OAc)2 and CuBr2 yielded 2-D 4-connected sql nets of 1 and 2 involving different coordination modes. A 63-hcb network of 3 was obtained between the 3-PPT ligand and CuBr2 with the in situ reduction of CuII–CuI and S–S oxidative coupling reactions.

Solvothermal reaction of a TCA (TCA = 4,4′,4′′-tricarboxytriphenylamine) ligand with Cd(NO3)2 yielded a unique 3D 12-connected metal–organic framework of 1, which can be simplified as a (3,3,12)-connected 3-nodal net with a Schläfli symbol of {416·636·814}{42·6}2{43}2 based on a 12-connected node of a pentanuclear Cd(II) cluster and a three-connected organic linker of TCA. Compound 1 exhibits both photoluminescence and proton conductivity. The luminescence properties of 1 originate from the triphenylamine chromophore of the TCA ligand. The proton conductivity of 1 is supposed to be relevant to the structure attributes of 1. On the one hand, the curved narrow channels lined with a hydrophilic pentanuclear Cd(II) cluster in 1 can improve the water affinity of framework and facilitate the water absorption under humid conditions. On the other hand, the coordinated water molecules within the pentanuclear Cd(II) cluster can produce a mobile H+ proton due to coordination activation. At 80 °C and 85% RH (relative humidity), compound 1 shows the proton conductivity of 1.45 × 10−6 S cm−1.

A class of π-conjugated organic synthons, namely 1, 3, 5-tris(2-alkylthiolpyrimidinyl)benzene (TMPB: alkyl = Me; TEPB: alkyl = Et; TPPB: alkyl = n-Pr) was designed and prepared, which only differ in the length of linear side chain. It was found that these organic synthons can keep a quasi-planar conformation even coordinated to metal ions due to intramolecular C–H⋯N hydrogen bonds. Assembly of these organic synthons with CuX2 (X = Cl, Br) generated four coordination polymers: [(TPPB)CuCl2]n (1), {[(TMPB)CuCl2]·H2O}n (2), [(TPPB)CuBr2]n (3), [(TEPB)CuBr2]n (4), among which 1–3 exhibit one-dimensional coordination ribbon structure and 4 shows a two-dimensional wave-like coordination network. Although 1–3 exhibit similar assembly hierarchy going from 1-D ribbon through 2-D supramolecular layer to 3-D supramolecular architecture, the side-chain-effect can be clearly seen which modulates intra-chain or inter-chain Cu⋯Cu distance; inter-chain C–H⋯S supramolecular interactions and even the co-existence of guest water molecules. The room-temperature direct-current (dc) conductivity of 1–4 is measured about 9.6 × 10−12 S cm−1, 2.9 × 10−9 S cm−1, 2.6 × 10−12 S cm−1 and 5.7 × 10−11 S cm−1, respectively, wherein the highest electronic conduction of 2 is assumed to be pertinent to the existence of unique inter-chain C–H⋯S interactions. Furthermore, the complex impedance technique reveals that 2 exhibits a alternate-current (ac) conductivity of 4.3 × 10−6 S cm−1 at room temperature, which almost decreases linearly with the rising temperature. The higher ac conductivity of 2 against its dc conductivity is assumed to be largely contributed by proton-conduction as the matter of fact that there exist in 2 guest water molecules and water-molecule-associated O–H⋯Cl hydrogen bonding network. The unusual temperature-dependent ac conductivity of 2 is possibly due to the temperature-sensitive O–H⋯Cl hydrogen bonding network, which is responsible for proton transporting.The side chains of quasi-planar π-conjugated organic synthons can modulate their assembled structures with CuX2 (X = Cl, Br), which further influence their conductive properties.

By the combination of different metal salts and solvents, four unprecedented in situ reactions have been discovered for heterocyclic disulfide of 2-ppds (2-ppds = di[4-(pyridin-2-yl)pyrimidinyl]disulfide). In the CH3CN–DMF solvent, reaction of 2-ppds with AgNO3 produced a one-dimensional chain structure of {[Ag2(1L)2]·2CH3CN}n (1), wherein 2-ppds was converted into its sulfonate of 1L by means of oxidative cleavage of the S–S bond. In the CH3CN–DCM solvent, reaction between 2-ppds and Cu(ClO4)2 yielded a discrete mononuclear Cu(II) coordination structure of [Cu(2L)2H2O)](ClO4)2 (2), of which 2-ppds was turned into a totally unexpected zwitterion product of 2Lvia C–S bond scission followed by O substitution. In the MeOH–DCM solvent, reaction of 2-ppds with Co(ClO4)2 resulted in a mononuclear Co(III) coordination structure of [Co(3L)2]ClO4·2CH3OH·H2O (3), in which 2-ppds was transformed into its persulfide of 3Lvia selective single C–S bond rupture. In the CH3CN–DMF solvent, reaction between 2-ppds and CuI afforded a binuclear mixed-valence CuICuII coordination structure of [Cu2I(4L)2] (4), wherein 2-ppds was converted into its thiolate of 4L through homolytic S–S bond cleavage. The reaction mechanisms of these reactions have also been discussed on the basis of these in situ generated coordination structures coupled with our previous observations on 2-ppds.

A two-dimensional (2D) layered structure 1 with (6,3) topology was constructed from Cu2I2 dimer and rigid conjugated tripodal tris-bidentate Schiff-base chelator L, wherein Cu2I2 dimer acts as a two-connecting inorganic node and L ligand works as a triangular three-connecting synthon. Compound 1 has been well structurally elucidated by single-crystal X-ray diffraction. Solid-state diffuse-reflectance UV–Vis spectra show that compound 1 exhibits a much lower optical band gap (Eg) of 1.85 eV compared to its individual components (Eg(CuI) = 3.1 eV, Eg(L) = 2.87 eV).

Assembly of di[4-(pyridin-3-yl)pyrimidinyl]disulfide (3-ppds) with different metal salts resulted in a variety of coordination polymers that were structurally elucidated. For MnCl2, a 1-D repeated rhomboidal chain structure [MnCl2(3-ppds)2]n (1) was obtained, whereas a 1-D helical chain structure [Zn(NO3)2(3-ppds)]n (2) was built from Zn(NO3)2. A 1-D zigzag chain structure [Cu2(OAc)4(3-ppds)]n (3) was produced from Cu(OAc)2. In all three complexes, the 3-ppds ligand plays the same role as a bis(monodentate) bridging linker but with variations in both C–S–S–C torsion angles and dihedral angles defined by its conjugated heteroaromatic rings (pyrimidine and pyridine). The luminescence properties of the complexes have been evaluated in the solid state.

Reaction of 4,4′-di(3-pyridyl-4-pyrimidinyl) disulfide (3-PPDS) with AgNO3 leads to a unique 2D extended structure {[Ag(3-PPDS)(NO3)]}n (1) based on [Ag2(3-PPDS)2] macrocycle units, of which 1D inorganic [Ag(NO3)]n helical chains are generated. By contrast, definite Ag–S bonding interactions associated with the disulfide function have been established in {[Ag(2-PPDS)]ClO4}n (2), which is assembled of 4,4′-di(2-pyridyl-4-pyrimidinyl) disulfide (2-PPDS) with AgClO4. Solid state luminescent properties of complexes 1 and 2 are also examined.Graphical abstractComplex 1 shows a unique 2D extended structure based on macrocycle units of which 1D purely inorganic [Ag(NO3)]n helical chains are formed, and complex 2 is a 1D chain structure with Ag–S bonding interactions.Highlights► A 2D extended structure based on macrocycle units and bridging NO3− anions. ► 1D inorganic [Ag(NO3)]n helical chains supported by disulfide ligand. ► Coordination bonding interactions between Ag+ and disulfide function.

Parallel comparative studies on reactivities of S–S function in 2-ppds (2-ppds = bis(4-(pyridin-2-yl)pyrimidin-2-yl)disulfane) have been carried out under the same thermolysis conditions. In the presence of FeCl2, thermolysis reaction of 2-ppds in the MeOH/CH2Cl2 mixture results in a mononuclear compound [FeCl2(2-pps)] with newly generated organic ligand 2-pps (2-pps = bis(4-(pyridin-2-yl)pyrimidin-2-yl)sulfane). In the absence of FeCl2, the result of solvolysis depends upon the conditions. Thus, in pure MeOH, 2-ppds partially converts into a mixture of S-(4-pyridin-2-yl)pyrimidin-2-yl (4-pyridin-2-yl)pyrimidine-2-sulfonothioate (2-ppst) and 2-pps, while in a MeOH/CH2Cl2 mixture, 2-(chloromethylthio)-4-(pyridin-2-yl)pyrimidine (2-ppct) is the main product.Parallel comparative studies show diverse reactions of S–S function in 2-ppds (2-ppds = bis(4-(pyridin-2-yl)pyrimidin-2-yl)disulfane) under both metal-mediated and metal-free thermolysis conditions.

Reactions of 4-PPDS (4-PPDS = 4,4′-di(4-pyridyl-4-pyrimidinyl)disulfide) with Zn(OAc)2 and FeCl2 produced a one-dimensional helical chain {[Zn(CH3CO2)2(4-PPDS)]·H2CO3}n (1) and a one-dimensional repeated rhomboidal coordination chain [FeCl2(4-PPDS)2]n (2), respectively. One-dimensional helical chain (1) is built from the alternating links of one Zn(II) ion and one 4-PPDS ligand with the same chirality whereas one-dimensional repeated rhomboidal chain (2) is constructed by alternated linking of one Fe(II) ion and two enantiomers of 4-PPDS ligands. Complex (1) has the unexpected carbonic acid in its crystal structure, which is assumed to be transformed from carbon dioxide. The solvent-accessible volume in complex (2) is approximate 151.4 Å3 per unit cell volume. Both complexes in the solid state exhibit intense photoluminescences with the emission maxima around 365 nm upon excitation at 260 nm.

An anionic zeolite-like metal–organic framework (AZMOF) with a twisted partially augmented the net, known as the “Moravia” net, [(CH3)2NH2]6[Sr13(O)3(BTTC)8(OH)2(H2O)16]·xS (Sr-BTTC, where S represents non-coordinated solvent molecules, and BTTC is the abbreviation of benzo-(1,2;3,4;5,6)-tris-(thiophene-2′-carboxylic acid)), has been solvothermally synthesized and characterized, which possesses an anionic framework and nano-sized sodalite cage. Through cation-exchange, Sr-BTTC is capable of uptaking large organic cationic dyes including Rhodamine B (RB), Basic Red 2 (BR2), Crystal Violet (CV) and Methylene Blue (MB), amongst which the adsorption capability for RB (up to 545 mg g−1), and BR2 (up to 675 mg g−1) is the highest for reported absorbants to date.

By the combination of different metal salts and solvents, four unprecedented in situ reactions have been discovered for heterocyclic disulfide of 2-ppds (2-ppds = di[4-(pyridin-2-yl)pyrimidinyl]disulfide). In the CH3CN–DMF solvent, reaction of 2-ppds with AgNO3 produced a one-dimensional chain structure of {[Ag2(1L)2]·2CH3CN}n (1), wherein 2-ppds was converted into its sulfonate of 1L by means of oxidative cleavage of the S–S bond. In the CH3CN–DCM solvent, reaction between 2-ppds and Cu(ClO4)2 yielded a discrete mononuclear Cu(II) coordination structure of [Cu(2L)2H2O)](ClO4)2 (2), of which 2-ppds was turned into a totally unexpected zwitterion product of 2Lvia C–S bond scission followed by O substitution. In the MeOH–DCM solvent, reaction of 2-ppds with Co(ClO4)2 resulted in a mononuclear Co(III) coordination structure of [Co(3L)2]ClO4·2CH3OH·H2O (3), in which 2-ppds was transformed into its persulfide of 3Lvia selective single C–S bond rupture. In the CH3CN–DMF solvent, reaction between 2-ppds and CuI afforded a binuclear mixed-valence CuICuII coordination structure of [Cu2I(4L)2] (4), wherein 2-ppds was converted into its thiolate of 4L through homolytic S–S bond cleavage. The reaction mechanisms of these reactions have also been discussed on the basis of these in situ generated coordination structures coupled with our previous observations on 2-ppds.

Solvothermal reaction of a TCA (TCA = 4,4′,4′′-tricarboxytriphenylamine) ligand with Cd(NO3)2 yielded a unique 3D 12-connected metal–organic framework of 1, which can be simplified as a (3,3,12)-connected 3-nodal net with a Schläfli symbol of {416·636·814}{42·6}2{43}2 based on a 12-connected node of a pentanuclear Cd(II) cluster and a three-connected organic linker of TCA. Compound 1 exhibits both photoluminescence and proton conductivity. The luminescence properties of 1 originate from the triphenylamine chromophore of the TCA ligand. The proton conductivity of 1 is supposed to be relevant to the structure attributes of 1. On the one hand, the curved narrow channels lined with a hydrophilic pentanuclear Cd(II) cluster in 1 can improve the water affinity of framework and facilitate the water absorption under humid conditions. On the other hand, the coordinated water molecules within the pentanuclear Cd(II) cluster can produce a mobile H+ proton due to coordination activation. At 80 °C and 85% RH (relative humidity), compound 1 shows the proton conductivity of 1.45 × 10−6 S cm−1.