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Three components, one pot synthesis of thiasalen/selenasalen Ni(II), Pd(II) and Pt(II) complexes, 14-19, by the oxidative addition of S-S/Se-Se bond of bis(o-formylphenyl)disulfide/-diselenide to Ni(0), Pd(0) and Pt(0) followed by in situ Schiff base formation with ethylenediamine is reported. S-S or Se-Se bonds were cleaved and coordinated to the metal center as thiolate (ArS(-)) or selenolate (ArSe(-)) while the formal oxidation state of metal centers was changed from '0' to '+2'. The disulfide/diselenide reacted with zero-valent metals at room temperature to give only the monometallic complexes. All complexes (except Pd-thiolate complex 15) were studied by single crystal X-ray crystallography and revealed the square planar geometry around metal centers.

Thiasalen podand 9 having S2N2 donor set has been synthesized by the condensation of 2-methylthiobenzaldehyde with ethylenediamine. The reaction of the thiasalen podand ligand with Pd(II) afforded two complexes depending on the reaction time. Shorter reaction time (5 min) afforded thioether complex 10; whereas with increase in reaction time (4 h) thioether-thiolate complex 11 was obtained via cleavage of one of the two S-C(Me) bonds of bis(methyl)thiasalen podand upon complexation. The reaction of 9 with Pt(II) afforded only thiolate-thioether complex 12 independent of the reaction time. The cleavage of both the S-C(Me) bonds of bis(methyl)thiasalen to afford bisthiolate complexes has never been observed. The structures of thiasalen podands and all three complexes have been determined by single crystal X-ray diffraction analysis. All three complexes possess a square planar geometry around the metal centres. Weak van der Waals interactions through C-H···F interactions are present in all three complexes leading to the formation of supramolecular synthons and the supramolecular structures are stabilized by aromatic π···π interactions, which leads to the formation of 3D pseudo-double helical network packing. Under similar conditions bis(methyl)salen did not form any complexes with Pd(II) and Pt(II).

Crystal engineering and supramolecular synthons approach are applied to synthesize a series of 2aminothiazole (and its methyl derivatives) salts/cocrystals with various dicarboxylic acids. On the basis of combinatorial library approach, 24 new salts/cocrystals of 2-aminothiazole and its methyl derivatives with various dicarboxylic acid (aliphatic unsaturated and saturated backbone) were synthesized and characterized. All the synthesized salts were subjected to gelation test in various solvents (polar and nonpolar). Interestingly, one of the salts/cocrystals, i.e., B3A6 (5methyl-2-aminothiazolium hydrogen decandioate) was found to be capable of immobilizing water at slightly higher minimum gelator concentration (MGC). A structure−property correlation between various cocrystals/salts based on single crystal X-structure of 11 compounds was undertaken. The gelation property of 2-aminothiazole-based gelling agent was found to be governed by the position of a methyl group on the thiazole ring, a length of the aliphatic carbon chain of dicarboxylic acid, and formation of hydrogen bonded network (HBN) leading to void in the single crystal structure. The comparison of single crystal X-ray structures of nongelators and a gelator were undertaken to understand the probable mechanism of hydrogelation in the series of 2-aminothiazole-based salts/cocrystals.

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