Non-covalent and Covalent Interactions of Anti-aromatic Isophlorinoids

Abstract

The thesis entitled “Non-covalent and Covalent Interactions of Anti-aromatic Isophlorinoids” is a study based on the anti-aromatic isophlorins. In an attempt to explore the reactivity of isophlorins, the thesis describes synthesis and characterization of non-covalent complexes obtained from π-π interaction between C60 fullerene and the π surface of the anti-aromatic macrocycle. In this endeavour, it was observed that the nature of the substituents on the macrocycle not only affects the strength of binding, but also induces dimerization of the macrocycle. Unlike aromatic porphyrins, the anti-aromatic isophlorins have electron deficient core and rich electron density at the periphery of the macrocycle. Prior to this work, there were no reports on non-covalent and covalent reactivity of this unique property of π system. This is mainly attributed to the limited number of stable and planar anti-aromatic isophlorins known to date. This thesis describes the synthesis and non-covalent interactions between the anti-aromatic π surface of stable and planar meso free isophlorins and the fullerene C60. The limited reactivity of the meso free carbons led to design the first covalent anti-aromatic dimer through a possible diradical intermediate. This unstable diradical isophlorin dimer could be stabilized with a diradical character upon expanding the macrocyclic skeleton to an expanded isophlorin through a systematic synthetic methodology. The products obtained from various reactions have been characterized unambiguously through experimental and computational studies. Quantum mechanical calculations were also employed for the better understanding aromatic and anti-aromatic characteristics of these molecules.