Computational Chemistry of Compounds with Donor-Acceptor Interactions

Compounds with donor-acceptor interactions find important applications in catalysis, C-H activation, phosphorus activation, selective oxidation and cyclization. Moreover, they are potential candidates for use in the synthesis of materials, polymers and light-harvesting systems. The efficient use of a chemical entity is possible when we know its structural and bonding properties. This computational study is intended for the same by studying in detail the structure and bonding properties of donor-acceptor complexes of heavier main-group metals with cyclophane ligands and some heterobimetallic complexes. Additionally, we explored the fluorescence characteristics of benzanthrone dyes. The first part (i.e. main group metal complexes) involves the exploration of structural features and thermal properties through DFT optimization and then calculating the change in enthalpy of formation for all the possibilities under consideration. For this purpose we selected the last three elements from each of Groups 13, 14 and 15 to explore their different coordination modes with two cyclophane ligands; [2.2.2]paracyclophane and deltaphane. We opted for chlorides of each metal to allow them to coordinate from outside the phenyl rings of the cyclophane cavity and from the top of the cavity. To see the coordination of the metals with the inner core of the selected cyclophanes, we put metal cations in the centre of the cavity and optimized. Subsequently, the bonding properties of these inclusion complexes have been analysed in detail on the basis of Morokuma-Ziegler energy decomposition analysis. Secondly, we investigated the structure and bonding properties of some indium-zinc heterobimetallic compounds through geometry optimization, NBO analysis and quantum theory of atoms in molecules (QTAIM) analysis--also known as Bader's analysis. We propose that the heterobimetallic reactant involves donor-acceptor bond that cleaves as a result of the addition of mesityl azide. The newly formed complex has In-N and Zn-N bonds. In the final part benzanthrone dyes containing intramolecular donor-acceptor interactions, (and hence, undergoing intramolecular charge transfer) were subject to the computational investigation of the mechanism of fluorescence taking place in them. Electronic excitations and the structure of first excited state in each case has been discussed thoroughly based on the time-dependent density functional theory. To check for the non-radiative loss of energy, we also performed calculations for the vertical excitations of the triplet states of all the molecules under study. To get a deeper insight into the intramolecular charge transfer, we performed NTO analysis that gives us information based on different colours in regions of charge accumulation and charge depletion.