DESIGN, SYNTHESIS AND PROPERTIES OF METAL COMPLEXES AND COORDINATION POLYMERS FOR [2+2] PHOTO CYCLOADDITION REACTIONS

Abstract

Synthesis of highly strained cyclobutane ring is of great interest for several decades. Among them, solid state synthesis is of immense important due to its high-yield and stereo selectivity through solvent less green synthetic procedure. Although the solid state [2+2] photoreactivity of organic compounds has been extensively investigated, the photoreactivity of metal complexes and coordination polymers (CPs) is not much explored, especially for the polymerization of metal complexes and in the transformation to higher dimensional CPs. In this dissertation several examples and different strategies to polymerize the metal complexes through photoreaction such as single step and step-wise photo polymerization reactions have been described. Interestingly, during the single step polymerization of metal complexes under UV, the crystals showed violent mechanical motions which are very similar to the popping of corn kernels on hot plate. This is a novel method to transform light into mechanical energy. Similarly during the two-step polymerization of metal complexes, dimerization of metal complexes followed by polymerization of dimer complexes has been observed. More interestingly, the transformation of monomer to dimer has been observed in single-crystal to single-crystal (SC-SC) manner which can also be reverted back by heating the single crystals in SC-SC manner. On the whole, this is a SC-SC-SC (SC3) transformation which is unprecedented in the literature. In addition, during the polymerization another metal complex, a very interesting ¿phenyl-olefin¿ photoreaction in solid state has been observed which was confirmed by SC-SC transformation along with other characterizations. This dissertation also describes the solid state transformation of coordination polymers from lower to higher dimensional structures. During the transformation of 1D to 2D CP, a fascinating two-step Host-Guest and Host-Host photoreaction has been observed. Besides all these, three highly porous 3D MOFs have been synthesized with wide 1D channels. Solvent induced structural dynamics have been studied by exchanging the lattice solvent in these compounds along with gas sorption studies. These gas sorption studies showed selective sorption of CO2 compared to all other gases. Hence these compounds can be used as gas separation materials.