Research Projects

Alkanes and alkenes are the fundamental classes of organic compounds that deal with the carbon-carbon single- and double-bonded motifs, respectively. These two classes of compounds are known for their various utility as materials from petroleum to the electronic industry. The carbon-carbon single bond in alkanes is constituted by the head-on overlap of two carbon-sp3-orbitals, whereas the carbon-carbon double bond is constituted by the simultaneous head-on overlap of two carbon-sp2-orbitals and the lateral overlap of two carbon-p-orbitals. As a result, removing valence electrons from the single bond of alkanes that is σ-electrons is not easy, unlike the removal from a double bond of alkenes that is of π-electrons, which makes alkanes more resistant to oxidation than alkenes. The other important aspect is the mode of removal of two degenerate valence electrons from carbon-carbon single and double bonds, whether it is sequential - one by one through the formation of radical-cation (for alkane: it would be one-electron sigma bond) vs. simultaneous - two at a time under the formation of carbocation/1,2-carbodication. In this regard, the recurring challenge for chemists is to make the electron-rich carbon-carbon single bonds and sequential oxidation of carbon-carbon double bonds under the formation of isolable radical cations. The potential utility for electron-rich carbon-carbon single bonds is to use them as organic electron donors (OEDs) for various chemical transformations and n-dopant for organic semiconductor. On the other hand, isolable radical cations can be judiciously assembled into diradicals and diradicaloids, even in high-spin systems. Considering these challenges and potential utility, we have been interested in synthesizing i) electron-rich carbon-carbon single bonds and ii) carbon-carbon double bond-derived radical-cation motifs to assemble open-shell molecules. This proposal aims to establish the synthesis of electron-rich carbon-carbon single bonds involving reducing the conjugate acid of double-carbene stabilized carbodicarbenes. The special emphasis will be on tuning their electron-releasing ability and efforts to make carbon-carbon single bonds extremely electron-rich. In the case of carbon-carbon double bond-derived radical-cation motifs under one-electron, we will proceed with involving various iminium cations, carbenes, and carbones, such that we would like to have their generation and subsequent survival at the wide range of electrochemical potentials, which will eventually help us to build the electronically diverse range of carbon-centered open-shell systems. At the same time, we can envision the synthesis of unprecedented heteronuclear open-shell systems. Quantum chemical calculations are essential to understand the electronic situations of all those electronically tuned carbon-carbon single- and double-bonds, accordingly will be performed to understand and address the electronic states in addition to comprehensive characterization of the synthesized molecules in the solution-state by (VT)-NMR spectroscopy and in the solid-state by single crystal X-ray structural analysis. In addition, quantum chemical calculations will be performed to develop the orbital-level understanding of the nature of carbon-carbon bonding, bond strengths, and spin densities in the high-spin molecules. Energy decomposition analysis (EDA) and atoms in molecules (AIM) will be performed to probe the bonding and hybridization on the central electron-rich carbon-carbon bonds. Multireference complete active space self-consistent field (CASSCF) and difference dedicated configuration interaction (DDCI) calculations will be performed to compute the relevant spin-Hamiltonian parameters (g-tensor, D-tensor, and A-tensors) and magnetic susceptibility behavior to probe the nature of radicals and magnetic interactions. The ground and excited states of the high-spin molecules will be analyzed through the CASSCF and TD-DFT calculations.