•Novel Cs complexes with lactose, d- and l-arabinose are reported.•X-ray diffraction, IR, FIR, THz and Raman results are presented.•New coordination structures are observed.The novel cesium chloride–lactose complex (CsCl·C12H22O10 (Cs-Lac), cesium chloride-d-arabinose and l-arabinose complexes (CsCl·C5H10O5, Cs-D-Ara and Cs-L-Ara) have been synthesized and characterized using X-ray diffraction, FTIR, FIR, THz and Raman spectroscopies. Cs+ is 9-coordinated to two chloride ions and seven hydroxyl groups from five lactose molecules in Cs-Lac. In the structures of CsCl-d-arabinose and CsCl-l-arabinose complexes, two kinds of Cs+ ions coexist in the structures. Cs1 is 10-coordinated with two chloride ions and eight hydroxyl groups from five arabinose molecule; Cs2 is 9-coordinated to three chloride ions and six hydroxyl groups from five arabinose molecules. Two coordination modes of arabinose coexist in the structures. α-d-arabinopyranose and α-l-arabinopyranose appear in the structures of Cs-D-Ara and Cs-L-Ara complexes. FTIR and Raman results indicate variations of hydrogen bonds and the conformation of the ligands after complexation. FIR and THz spectra also confirm the formation of Cs-complexes. Crystal structure, FTIR, FIR, THz and Raman spectra provide detailed information on the structure and coordination of hydroxyl groups to metal ions in the cesium chloride–lactose, cesium chloride-D- and l-arabinose complexes.

The novel coordination structures of europium and terbium chloride-picolinamide complexes (EuCl3·(C6H6N2O)2·5H2O, Eu-pa and TbCl3·(C6H6N2O)2·5H2O, Tb-pa) are reported. The crystal structures in the solid state are characterized by X-ray single crystal diffraction, FTIR, Raman, FIR, THz and luminescence spectroscopy. In the crystal structures, the pyridyl nitrogen and carbonyl oxygen atoms in picolinamide are coordinated to the metal ions to form a five-membered ring structure. The experimental results indicate the similar coordination structures of Eu and Tb-pa complexes and the changes of hydrogen bonds and conformation of the ligands induced by complexation. The results provide models for the coordination structures of lanthanide ions with ligands having amide groups.The crystal structures, FTIR, Raman, FIR, THz and luminescence spectroscopy are presented for Eu and Tb-picolinamide complexes.

•Novel Co and Sr complexes with three isomers are reported.•The ligands are nicotinamide, isonicotinamide and picolinamide.•X-ray diffraction, IR, FIR, THz, Raman and UV–Vis results are presented.•New coordination structures are observed.Novel coordination structures formed by cobalt(II) and strontium(II) complexes with nicotinamide (na), isonicotinamide (ina) and picolinamide (pa) are reported. The structures of these complexes (CoCl2·(C6H6N2O)2·6H2O (Co-na), CoCl2·(C6H6N2O)2 (Co-ina), CoCl2·(C6H6N2O)2·2H2O, (Co-pa), SrCl2·(C6H6N2O)2·4H2O (Sr-na), SrCl2·(C6H6N2O)2·3H2O (Sr-ina) and SrCl2·C6H6N2O·H2O (Sr-pa)) in the solid state have been characterized by X-ray single crystal diffraction, FTIR, FIR, THz, Raman and UV–Vis spectroscopies. Pyridyl nitrogen of nicotinamide is coordinated to Co2+, but pyridyl nitrogen and carbonyl oxygen are used for coordination to Sr2+, and each Sr2+ is coordinated to four ligands. For isonicotinamide, pyridyl nitrogen is coordinated to Co2+, carbonyl oxygen is coordinated to Sr2+ and the ligand is also hydrogen-bonded in Sr-ina. Pyridyl nitrogen and carbonyl oxygen of picolinamide are coordinated to Co2+ to form a five-membered ring structure, but the carbonyl oxygen is coordinated to two Sr2+ ions in Sr-pa. Some of the complexes can form chain or network structures. The experiments results indicate the differences of the coordination of Co and Sr ions, the changes of hydrogen bonds and conformation of the ligands induced by complexation.Graphical abstractNovel cobalt(II) and strontium(II) complexes with nicotinamide (na), isonicotinamide (ina) and picolinamide (pa) complexes are reported. New coordination structures were observed.

•We applied the DAOSD approach to probe weak coordination between Co2+ and acetone.•Subtle spectral variation on carbonyl band and d–d transition band are revealed.•The spectral variation suggests coordination occur between acetone and Co2+.•Coordination between acetone and Co2+ is further confirmed by EXAFS results.We applied a newly developed technique of the DAOSD (Double Asynchronous Orthogonal Sample Design) approach to probe weak coordination between Co2+ ions and acetone. Subtle spectral variation on the carbonyl band of acetone and d–d transition band are revealed via cross peaks of 2D asynchronous spectra generated by using the DAOSD approach. These results suggest that coordination occur between cobalt ions and the carbonyl group of acetone. To confirm whether coordination occur between cobalt ions and acetone, EXAFS experiments are utilized. The EXAFS results reveal that a Co2+ is coordinated by six methanol molecules in anhydrous CoCl2/methanol solution. Upon addition of acetone in into the anhydrous CoCl2/methanol solution, the coordination number of Co2+ ion becomes four, and one coordinating oxygen atom is replaced by a chlorine atom. We infer that the decrease in coordination number of Co2+ ion is due to the participation of the carbonyl oxygen of acetone in the coordination since the size of acetone is larger than methanol. This result provides an alternative evidence to support the conclusion that Co2+ ions coordinate with acetone, which is separately obtained from the 2D asynchronous spectra generated by using the DAOSD approach.

The novel cesium chloride–d-ribose complex (CsCl·C5H10O5; Cs-R) and cesium chloride–myo-inositol complex (CsCl·C6H12O6; Cs-I) have been synthesized and characterized using X-ray diffraction and FTIR, FIR, THz, and Raman spectroscopy. Cs+ is eight-coordinated to three chloride ions, O1 and O2 from one d-ribose molecule, O1 from another d-ribose molecule, and O4 and O5 from the third d-ribose molecule in Cs-R. For one d-ribose molecule, the oxygen atom O1 in the ring is coordinated to two cesium ions as an oxygen bridge, O2 is cocoordinated with O1 to one of the two cesium ions, and O4 and O5 are coordinated to the third cesium ion, respectively. O3 does not coordinate to metal ions and only takes part in forming hydrogen bonds. One chloride ion is connected to three cesium ions. Thus, a complicated structure of Cs–d-ribose forms. For Cs-I, Cs+ is 10-coordinated to three chloride ions, O1 and O2 from one myo-inositol molecule, O3 and O4 from another myo-inositol molecule, O5 and O6 from the third myo-inositol molecule, and O6 from the fourth myo-inositol molecule. One metal ion is connected to four ligands, and one myo-inositol is coordinated to four Cs+ ions, which is also a complicated coordination structure. Crystal structure results, FTIR, FIR, THz, and Raman spectra provide detailed information on the structure and coordination of hydroxyl groups to metal ions in the cesium chloride–d-ribose and cesium chloride–myo-inositol complexes.

•Lanthanide–isonicotinamide complexes were synthesized and characterized.•X-ray diffraction, IR, FIR, THz and Luminescence results were presented.•Four kinds of structures, with or without chloride coordination in the coordination spheres were observed for lanthanide–isonicotinamide complexes.The coordination of amide groups to metal ions is important because it may be involved in the interactions between metal ions and proteins. The synthesis and characterization of nine novel lanthanide–isonicotinamide (ina) complexes, including LaCl3, PrCl3, NdCl3, SmCl3, EuCl3, GdCl3, TbCl3, ErCl3 and PrBr3 complexes are reported. The structures of these complexes in the solid state have been characterized by X-ray single crystal diffraction, FTIR, FIR, THz and Luminescence spectroscopy. Isonicotinamide has only one coordination mode in four structures as O-monodentate ligand to coordinate to metal ions, but four kinds of topological structures are observed for lanthanide–isonicotinamide complexes, including LnCl3⋅(C6H6N2O)2⋅4H2O (La, Pr, Nd and Sm), EuCl3⋅(C6H6N2O)2⋅7H2O, LnCl3⋅(C6H6N2O)2⋅6H2O (Gd, Tb and Er) and PrBr3⋅(C6H6N2O)2⋅7H2O. Chloride ions can coordinate to metal ions or hydrogen-bonded. FTIR spectra indicate the formation of four kinds of lanthanide–ina complexes, the extensive hydrogen bond networks after complexation and the coordinations and the changes of the conformation of the ligand. FIR and THz spectra also confirm the formation of lanthanide ion–ina complexes. Luminescence spectra of Eu and Tb-ina complexes have the characteristics of Eu and Tb ions.Four kinds of structures, with or without chloride coordination in the coordination spheres were observed for lanthanide–isonicotinamide complexes.

The coordination of carbohydrate to metal ions is important because it may be involved in many biochemical processes. The synthesis and characterization of several novel lanthanide-erythritol complexes (TbCl3·1.5C4H10O4·H2O (TbE(I)), Pr(NO3)3·C4H10O4·2H2O (PrEN), Ce(NO3)3·C4H10O4·2H2O (CeEN), Y(NO3)3·C4H10O4·C2H5OH (YEN), Gd(NO3)3·C4H10O4·C2H5OH (GdEN)) and Tb(NO3)3·C4H10O4·C2H5OH (TbEN) are reported. The structures of these complexes in the solid state have been determined by X-ray diffraction. Erythritol is used as two bidentate ligands or as three hydroxyl group donor in these complexes. FTIR spectra indicate that two kinds of structures, with water and without water involved in the coordination sphere, were observed for lanthanide nitrate-erythritol complexes. FIR and THz spectra show the formation of metal ion-erythritol complexes. Luminescence spectra of Tb-erythritol complexes have the characteristics of the Tb ion.

Three novel lanthanum chloride–erythritol complexes (LaCl3·C4H10O4·5H2O (LaE(I)), LaCl3·C4H10O4·3H2O (LaE(II)), and LaCl3·1.5C4H10O4 (LaE(III)) were synthesized and characterized by single crystal X-ray diffraction, FTIR, far-IR, THz, and Raman spectroscopy. The coordination number of La3+ is nine. LaE(I) and LaE(II) have similar coordination spheres, but their hydrogen bond networks are different. Erythritol exhibits two coordination modes: two bidentate ligands and tridentate ligands in LaE(III). Chloride ions and water coordinate with La3+ or participate in the hydrogen-bond networks in the three complexes. Crystal structures, FTIR, FIR, THz, and Raman spectra provide detailed information on the structures and coordination of hydroxyl groups to metal ions in the metal–carbohydrate complexes.Graphical abstractHighlights► Five lanthanide chloride erythritol complexes are reported in the literature. ► Three new LaCl3–erythritol complexes have been synthesized and characterized. ► X-ray diffraction, IR, FIR, THz, and Raman results are presented.

This paper introduces a new approach called double asynchronous orthogonal sample design (DAOSD) to probe intermolecular interactions. A specifically designed concentration series is selected according to the mathematical analysis to generate useful 2D correlated spectra. As a result, the interfering portions are completely removed and a pair of complementary sub-2D asynchronous spectra can be obtained. A computer simulation is applied on a model system with two solutes to study the spectral behavior of cross peaks in 2D asynchronous spectra generated by using the DAOSD approach. Variations on different spectral parameters, such as peak position, bandwidth, and absorptivity, caused by intermolecular interactions can be estimated by the characteristic spectral patterns of cross peaks in the pair of complementary sub-2D asynchronous spectra. Intermolecular interactions between benzene and iodine in CCl4 solutions were investigated using the DAOSD approach to prove the applicability of the DAOSD method in real chemical system.

The interactions between metal ions and hydroxyl groups of carbohydrates are important for their possible biological activities. Here two HoCl3–galactitol complexes ([Ho(galac)(H2O)3)]Cl3·0.5galac) (HoG(I)) and ([Ho2(galac)(H2O)12)]Cl6·2H2O) (HoG(II))) and one ErCl3–galactitol complex ([Er(galac)(H2O)3)]Cl3·0.5galac)(ErG)) were prepared and characterized. The possible structures of HoG(I) and ErG were deduced from FTIR, elemental analysis, ESI-MS, FIR, THz and TGA results. It is suggested that Ho3+ or Er3+ is 9-coordinated with six hydroxyl groups from two galactitol molecules and three water molecules, and another galactitol molecule is hydrogen-bonded in HoG(I) and ErG and the ratio of metal to ligand is 1:1.5. The structure of HoG(II) was determined by FTIR and X-ray diffraction analyses. The results demonstrate that lanthanide ions with galactitol may form two compounds in a system and different topological structures can be obtained.Highlights► The coordination between metal ion and carbohydrates are important. ► Two HoCl3, one ErCl3–galactitol complex were prepared. ► Structures of HoG(I) and ErG were deduced from IR, FIR, THz, TGA and ESI-MS spectra. ► The X-ray crystal structure of HoG(II) was determined.

In this paper several polycrystalline molecules with sulfonate groups and some of their metal complexes, including dl-homocysteic acid (DLH) and its Sr- and Cu-complexes, pyridine-3-sulphonic acid and its Co- and Ni-complexes, sulfanilic acid and l-cysteic acid were investigated using THz time-domain methods at room temperature. The results of THz absorption spectra show that the molecules have characteristic bands in the region of 0.2–2.7 THz (6–90 cm−1). THz technique can be used to distinguish different molecules with sulfonate groups and to determine the bonding of metal ions and the changes of hydrogen bond networks. In the THz region DLH has three bands: 1.61, 1.93 and 2.02 THz; and 0.85, 1.23 and 1.73 THz for Sr-DLH complex, 1.94 THz for Cu-DLH complex, respectively. The absorption bands of pyridine-3-sulphonic acid are located at 0.81, 1.66 and 2.34 THz; the bands at 0.96, 1.70 and 2.38 THz for its Co-complex, 0.76, 1.26 and 1.87 THz for its Ni-complex. Sulphanilic acid has three bands: 0.97, 1.46 and 2.05 THz; and the absorption bands of l-cysteic acid are at 0.82, 1.62, 1.87 and 2.07 THz, respectively. The THz absorption spectra after complexation are different from the ligands, which indicate the bonding of metal ions and the changes of hydrogen bond networks. M–O and other vibrations appear in the FIR region for those metal–ligand complexes. The bands in the THz region were assigned to the rocking, torsion, rotation, wagging and other modes of different groups in the molecules. Preliminary assignments of the bands were carried out using Gaussian program calculation.

In this work, THz absorption spectra of some saccharides and their metal complexes were measured. The main purpose of this work is to investigate the M–O vibrations, intermolecular and intramolecular hydrogen bonds and other vibrations in the FIR region using powerful spectroscopic techniques adopting the metal–sugar complexes prepared in our laboratory. The M–O vibrations in the FIR spectra of metal–sugar complexes indicate the formation of metal complexes. The THz spectrum of glucose below 100 cm−1 was measured at first to confirm the THz experimental method. Characteristic absorption bands in the spectra of various samples are observed. THz spectra of saccharides below 100 cm−1 often have several absorption bands, and different saccharides have various absorption peaks in the THz region, which may be used to distinguish different saccharides. The differences in the number of bands observed are related to different structures of the samples, and these absorption bands are related to the collective motion of molecules. But the THz spectra of their metal complexes are different from the ligands, and no band appears in the region below 50 cm−1 at the present experimental condition, which indicates that THz spectroscopy may also be helpful to identify the formation of metal–sugar complexes, and the changes after complexation in the THz spectra below 100 cm−1 may be related to different metal ions. The metal–sugar complexes with similar crystal structures resemble mid-IR spectra, but their THz spectra may have some differences.