Five novel zinc(II) and cadmium(II)
β-oxodithioester complexes,
[Zn(L1)2] (1), [Zn(L2)2]
n
(2), [Zn(L3)2]
n
(3) [Cd(L1)2]
n
(4), [Cd(L2)2]
n
(5), with β-oxodithioester ligands, where L1 = 3-(methylthio)-1-(thiophen-2-yl)-3-thioxoprop-1-en-1-olate, L2 = 3-(methylthio)-1-(pyridin-3-yl)-3-thioxoprop-1-en-1-olate,
and L3 = 3-(methylthio)-1-(pyridin-4-yl)-3-thioxoprop-1-en-1-olate,
were synthesized and characterized by elemental analysis, IR, UV–vis,
and NMR spectroscopy (1H and 13C{1H}). The solid-state structures of all complexes were ascertained
by single-crystal X-ray crystallography. The β-oxodithioester
ligands are bonded to Zn(II)/Cd(II) metal ions in an O∧S and N chelating/chelating–bridging fashion leading to the
formation of 1D (in 2–4) and 2D (in 5) coordination polymeric structures, but complex 1 was obtained as a discrete tetrahedral molecule. Complex 4 crystallizes in the C2 chiral space group and has
been studied using circular dichroism (CD) spectroscopy. The multidimensional
assemblies in these complexes are stabilized by many important noncovalent
C–H···π (ZnOSC3, chelate),
π···π, C–H···π,
and H···H interactions. The catalytic activities of 1–5 in reactions involving C–C
and C–O bond formation have been studied, and the results indicated
that complex 3 can be efficiently utilized as a heterogeneous
bifunctional catalyst for the Knoevenagel condensation and multicomponent
reactions to develop biologically important organic molecules. The
luminescent properties of complexes were also studied. Interestingly,
zinc complexes 1–3 showed strong
lumniscent emission in the solid state, whereas cadmium complexes 4 and 5 exhibited bright luminescent emission
in the solution phase. The semiconducting behavior of the complexes
was studied by solid-state diffuse reflectance spectra (DRS), which
showed optical band gaps in the range of 2.49–2.62 eV.