A Spectroscopic Method for Distinguishing Two Novel Sandwich-Type Tungsten Oxide Cluster Compounds

This study introduces two novel sandwich-type tungsten-oxygen cluster compounds synthesized by hydrothermal methods, H4(C6H12N2H2)3{Na(H2O)2[Mn2(H2O)(GeW9O34)]}2 (Compound 1) and H2(C6H12N2H2)3.5{Na3(H2O)4[Co2(H2O)(GeW9O34)]2}·17H2O (Compound 2). The two compounds comprise cluster anions [GeW9O34]10- coordinated with transition metal atoms, either Mn or Co, and are stabilized by organic ligands. These compounds are crystallized in the hexagonal crystal system and P63/m space group. The two compounds were characterized through various techniques. Fourier transform infrared (IR) spectroscopy showed absorption peaks of anionic backbone vibrations of the Keggin cluster at 500-1000 cm-1, IR spectral peaks of δ(N-H) and νas(C-N) of the ligand triethylenediamine at 1000-2000 cm-1, and IR spectral peaks of the ligand νas(N-H) and νas(O-H) of water at 3000-3500 cm-1. Despite similar one-dimensional (1D) IR spectra due to the same cluster anions and similar molecular structures, the two compounds exhibited distinct responses in two-dimensional correlation spectroscopy with IR under magnetic and thermal perturbations. Under magnetic perturbation, Compound 1 showed a strong response peak for νas(W-Ob-W), while Compound 2 exhibited a strong response peak for νas(W=Od), possibly linked to differing magnetic particles. Similarly, Compound 1 displayed a strong response peak under thermal perturbation for νas(W-Oc-W). In contrast, Compound 2 showed a strong response peak for νas(W=Od); these results may be attributed to the different hydrogen bonding connections between the two compounds, which affect the groups in distinct ways through vibration and transmit these vibrations to the W-O bonds. The research presented in this paper expands the theoretical and experimental data of 2D correlation IR spectroscopy.

Design and Solvothermal Synthesis of Polyoxometalate-Based Cu(II)-Pyrazolate Photocatalytic Compounds for Solar-Light-Driven Hydrogen Evolution

Polyoxometalates (POMs) are known for their photocatalytic hydrogen production activity, but their solubility and limited stability often restrict their practical applications. Herein, we designed and solvothermally synthesized two new Cu-H₂bpz (3,3',5,5'-tetramethyl-4,4'-bipyrazole, abbreviated as H₂bpz) compounds, namely, Cu_0.5(H₂bpz)(NO₃) (1) and Cu(Hbpz)(Cl)·DMF (2), and three new polyoxometalate-based Cu(II)-pyrazolate compounds, namely, Cu(PW₁₂O₄₀)_0.5(H₂bpz)₂(H₂O)·(OH)_0.5(H₂O)_5.5 (3), Cu(HPMo₁₂O₄₀)(H₂bpz)₂(H₂O)₂·(H₂O)₄ (4), and Cu₂(SiW₁₂O₄₀)(H₂bpz)₃(H₂O)₃·(H₂O)₆ (5). Compound 3 (Cu(PW₁₂O₄₀)_0.5(H₂bpz)₂(H₂O)·(OH)_0.5(H₂O)_5.5) exhibits the best photocatalytic activity of 44.4 μ L h^-1 g^-1, which may be related to the stability of compounds. Herein, the solvothermal method has been proven to be an effective method in synthesizing stable organic-inorganic hybrid compounds with soluble POMs, metal ions, and organic ligands. Thus, heterogeneous catalysts with outstanding solar-light-driven photocatalytic properties were obtained.

All inorganic coordination polymers have been made possible with the m-carboranylphosphinate ligand

New examples of 1D coordination polymers (CPs) and complexes containing the purely inorganic carboranylphosphinate ligand [1-OPH(O)-1,7-closo-C2B10H11]- are reported. The reaction of Na[1-OPH(O)-1,7-closo-C2B10H11] salt with MCl2 (M = Mn, Co, Ni, Cu, Zn and Cd) in MeOH or EtOH leads to compounds 1-8. All compounds have been exhaustively characterized by analytical and spectroscopic techniques. X-ray analysis and spectroscopy characterization revealed the differences between the isolated compounds: 1D polymeric chains (CPs) with carboranylphosphinate ligand bridges have been obtained with MnII, CdII or ZnII centres, whereas compounds with low nuclearity have been isolated with CuII, CoII and NiII. No polymeric structures were obtained in the CoII and NiII complexes due to the higher affinity of these metals for water than that for the m-carboranylphosphinate and accordingly, these complexes generate supramolecular hydrophobic/hydrophilic structures. The reactivity of manganese polymer 1 with water leads to the breakage of the polymer with the formation of a new mononuclear compound 2, and that in methanol leads back to the initial polymer 1. However, the reactivity of polymer 1 with 2,2'-bpy maintains the core present in the initial polymer, leading to the CP 3, which in methanol/water medium produces species of lower nuclearity. The magnetic properties of the compounds studied show weak antiferromagnetic coupling.

Tubular Hybrids: A Nanoparticle-Molecular Network

We report here a new methodology for the formation of freestanding nanotubes composed of individual gold nanoparticles (NPs) cross-linked by coordination complexes or porphyrin molecules using WS₂ nanotubes (INT-WS₂) as a template. Our method consists of three steps: (i) coverage of these robust inorganic materials with monodispersed and dense monolayers of gold NPs, (ii) formation of a molecular AuNP network by exposing these decorated tubes to solutions containing a ruthenium polypyridyl complex or meso-tetra(4-pyridyl)porphyrin, and (iii) removal of the INT-WS₂ template with a hydrogen peroxide solution. Nanoindentation of the template-free AuNP tubes with atomic force microscopy indicates a radial elastic modulus of 4 GPa. The template-free molecular AuNP tubes are characterized using scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, and micro-Raman spectroscopy. The methodology provides a convenient and scalable strategy for the realization of molecular AuNP tubes with a defined length and diameter, depending on the dimensions of the template.

Advanced Cd(II) complexes as high efficiency co-sensitizers for enhanced dye-sensitized solar cell performance

This work reports on two new complexes with the general formula [Cd3(IBA)3(Cl)2(HCOO)(H2O)]n (1) and {[Cd1.5(IBA)3(H2O)6]·3.5H2O}n (2), which can be synthesized by the reaction of Cd(II) with rigid linear ligand 4-HIBA containing imidazolyl and carboxylate functional groups [4-HIBA = 4-(1H-imidazol-1-yl)benzoic acid]. Single-crystal X-ray diffraction analyses indicate that complex 1 is a 2D "wave-like" layer structure constructed from trinuclear units and complex 2 is just a mononuclear structure. Surprisingly, both complexes 1 and 2 appear as a 3D supramolecular network via intermolecular hydrogen bonding interactions. What's more, due to their strong UV-visible absorption, 1 and 2 can be employed as co-sensitizers in combination with N719 to enhance dye-sensitized solar cell (DSSC) performance. Both of them could overcome the deficiency of the ruthenium complex N719 absorption in the region of ultraviolet and blue-violet, and the charge collection efficiency is also improved when 1 and 2 are used as co-sensitizers, which are all in favor of enhancing the performance. The DSSC devices using co-sensitizers of 1/N719 and 2/N719 show an overall conversion efficiency of 8.27% and 7.73% with a short circuit current density of 17.48 mA cm(-2) and 17.39 mA cm(-2), and an open circuit voltage of 0.75 V and 0.74 V, respectively. The overall conversion efficiency is 27.23% and 18.92% higher than that of a device solely sensitized by N719 (6.50%). Consequently, the prepared complexes are high efficiency co-sensitizers for enhancing the performance of N719 sensitized solar cells.