Synthesis, structure and properties of inorganic-organic hybrid compounds

Abstract

Synthesis, structure, photodimerization, structural transformation and photocatalytic studies have been carried out on a family of cadmium thiosulfate compounds with varying dimensionalities. The observation of unique Cd?S? clusters, and 4?fold interpenetrated diamondoid structures in the three?dimensional compound is noteworthy. We observed a structural transformation as a function of time, the two?dimensional compound II readily transforms to the more stable three?dimensional compound III. The structural transformations were observed in photochemical reactions, the formation of a one?dimensional structure (Ia) from the molecular complexes of I and rigid cyclized products in II and III. This shows that the photochemical reactions were facile in the above compounds. The photochemical method provides a viable alternative for the structural modification through post?synthetic route in inorganic–organic hybrid compounds. The prepared compounds exhibit reasonable activity as a photocatalyst. When compared, the present study along with our earlier studies clearly indicates that the chemistry of the tetrahedral thiosulfate ions provides avenues for further research. Four new zinc thiosulfate?based hybrid compounds [Zn(S?O?)(tpp)] I, [Zn?(S?O?)?(bpy)?] II, [Zn(S?O?)(6pe)]·H?O III and [Zn?(S?O?)?(6pa)?]·3H?O IV have been successfully synthesized and characterized. Compound I exhibits two?dimensional structure and the rest of the compounds II, III and IV exhibit three?dimensional structure. All the compounds exhibit 3?fold interpenetration in their structures. The compounds exhibit reasonable proton mobility at room temperature, photocatalytic dye degradation under UV radiation and all the compounds have reasonable Lewis acid catalytic behavior. The number of available thiosulfate?based hybrid structures is limited and the present solids provide important members to this class of compounds. The present study indicates that it may be profitable to investigate other unusual anions such as dichromate, chromate etc. Two new cobalt dichromate?based inorganic–organic hybrid compounds have been prepared and characterized. Both the compounds have one?dimensional cobalt dichromate chains connected with organic ligands forming the three?dimensional structure. To the best of our knowledge, this is the first report of cobalt dichromate stabilized in a three?dimensional hybrid structure. The electrochemical water oxidation reaction, carried out employing the cobalt dichromate hybrids, indicates good OER activity. The compounds were found to be stable up to 100 cycles under the operating conditions without loss of OER activity. It is clear that the compounds of this type are important for exploring new electrocatalysts in OER reactions. Two new Cu(I) compounds [Cu?(6ds)(6py)?]·2H?O (I), and [Cu?(6ds)?(o2py)?]·6H?O (III), and four Ag(I) compounds [Ag?(6ds)(6py)?]·2H?O (II), [Ag?(6ds)(qzpy)?]·4H?O (IV), [Ag(6ds)½(6pe)]·3H?O (V), and [Ag?(6ds)?(6pp)?]·9H?O (VI), have been synthesized and characterized by different techniques. We found that compounds I and II exhibit one?dimensional structure, whereas III and IV (having the same ligand system) are two?dimensional structures. Compound V has a similar ligand system to IV but has a one?dimensional structure which extends to form a double?layer two?dimensional sheet by weak interactions. An interpenetrated 3D structure is formed by employing flexible ligands in VI. In the case of V, [2+2] photodimerization in the solid state occurred because of argentophilic interactions which guide the stacking of olefins in the coordination polymer. The emission spectra of the compounds have been studied in solid states and show strong emission bands at ~394 nm which are ligand?centered. Anion?exchange study was carried out using perchlorate and permanganate in all of the compounds. Among these, only compound II shows a reversible anion exchange, whereas the others (I, III–VI) show an irreversible anion exchange for perchlorate. In addition, compound II has unsaturated coordination metal sites which exhibit reasonable Lewis acid catalysis.