Four new dicyanamide (dca) bridged multinuclear Zn(II)-Schiff-base complexes, {[Zn2L(1)(μ1,5-dca)dca]·CH3OH}2 (1), [Zn2L(2)(μ1,5-dca)dca]n (2), [Zn3L(3)2(μ1,5-dca)2]n (3), and [(ZnL(4))2Zn(μ1,5-dca)dca]n (4), have been synthesized using four different Schiff bases L(1)H2 = N,N(/)-bis(3-methoxysalicylidenimino)-1,3-diaminopentane, L(2)H2 = N,N'-bis(5-bromo-3-methoxysalicylidenimino)-1,3-diaminopropane, L(3)H2 = N,N'-bis(5-bromosalicylidenimino)-1,3-diaminopropane, and L(4)H2 = N,N'-bis(5-chlorosalicylidenimino)-1,3-diaminopropane and NaN(CN)2 in order to extend the metal-ligand assembly. The directional properties of linear end-to-end bridging dca ligands have resulted in different metal ion connectivities leading to unique variety of templates in each of the complexes. All the ligands and complexes have been characterized by microanalytical and spectroscopic techniques. The structures of the complexes have been conclusively determined by single crystal X-ray diffraction studies. Thermogravimetric analyses have been performed to investigate the thermal stability of the metal-organic frameworks. Finally, the photoluminescence properties of the complexes as well as their respective ligands have been investigated with a comparative approach.

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The hydrazone Schiff base ligands (E)-NЈ-(2-hydroxybenzylidene)acetohydrazide (HL 1 ) and (E)-NЈ-(2,3-dihydroxybenzylidene)acetohydrazide (H 2 L 2 ) with a functional group variation in the aromatic moiety have been synthesized. The ligands have been used to synthesize the following Mn II complexes: the mononuclear complex [Mn(HL 1 ) 2 ]-[ClO 4 ] 2 ·2H 2 O (1), the cocrystallized discrete dinuclear complex {[Mn(HL 1 ) 2 ]·[Mn(L 1 ) 2 ]}[ClO 4 ] 2 (2), and the phenoxidobridged dinuclear complex [Mn(μ-HL 2 )(H 2 O)] 2 [ClO 4 ] 2 (3). The ligands and the complexes were characterized by FTIR [a]

Three new hetero-bimetallic coordination complexes [Na-(CuIIL1)2](ClO4)·0.5H2O (1), [Na(CuIIL2)2][CuI2(μ1,3-NCS)3]n\ud (2), and {[Na(CuIIL3)2](μ1,5-dca)}n (3; dca = dicyanamide) have been synthesized by using different Schiff base ligands [e.g., L1H2 = N,N=-bis(3-methoxysalicylidenimino)-1,3-diaminopentane, L2H2 = N,N=-bis(3-ethoxysalicylidenimino)- 1,3-diaminopropane, and L3H2 = N,N=-bis(5-bromo-3-methoxysalicylidenimino)-1,3-diaminopropane] in the presence\ud of pseudohalide coligands N3–, SCN–, and N(CN)2– (dca),respectively. The ligands and the complexes have been characterized\ud by microanalytical and spectroscopic techniques. The structures of the complexes, determined by single-crystal X-ray diffraction studies, show that in all cases a trinu-clear Na(CuIIL)2 unit is formed, but of different configurations. 1 does not include N3– anions. In contrast, in 2, SCN– extrudes partial in situ reduction of CuII to lead to the formation of an infinite [CuI\ud 2(μ1,3-NCS)3]n anionic chain; and in 3, N(CN)2– bridges the metal–ligand assemblies to form a 1D polymeric chain. ESI-MS, UV/Vis spectroscopy, and cyclic voltammetry were performed to investigate the solution-state behavior of the complexes. Theoretical calculations of the optimized geometries of the complexes were carried out at the BLYP/DNP level to determine their relative stabilities from the HOMO–LUMO gap and chemical softness values

A potentially hexadentate N 2 O 4 donor Schiff base ligand N,N ¤ -bis(5-bromo-3-methoxysalicylideneimino)-1,3diaminopropane (H 2 L 1 ) has been used to synthesize two mononuclear coordination complexes [Cu(L 1 )]¢H 2 O (1) and [Co(L 1 )(HL 2 )]ClO 4 ¢CH 3 CN (2). The cobalt complex is a unique mixed-ligand species comprising both the di-and monocondensed ligands; the latter (HL 2 ) resulted from in situ hydrolytic cleavage of H 2 L 1 . Ligand L 1 assumes a planar arrangement in 1 and a folded β-cis configuration in 2, induced in this case by the chelating HL 2 ligand. The complexes are characterized by elemental analyses, FT-IR, and UVvis spectral methods, and their structures are established by single-crystal X-ray diffraction study. Both the complexes are proven to be efficient catalysts for the epoxidation of alkenes by H 2 O 2 or PhIO. The efficiency of alkene epoxidation is however somewhat superior with PhIO, and in each case, 2 appears to be a slightly better catalyst than 1.