In Silico Studies in Exploiting Weak Noncovalent C-H~+···π and π-π Interactions To Achieve Dual Properties: Hyperbasicity and Multiple Dihydrogen Storage Materials with Paracyclophane-Based Carbene Derivatives

摘要

This work reports that noncovalent interactions can be exploited to achieve hyperbasicity of a base. A new class of superbase has been identified using paracyclophane-based carbenes that possess a proton affinity (PA) value of 1251.4 kJ/mol at the M06-2X/6-311+G~(**)/7B3LYP/6-31+G~* level of theory. Noncovalent interactions such as C-H~+···π and through-space π-π interactions amplify the basicity of such carbene systems by the stabilization of their protonated forms. These paracyclophane systems can be a suitable candidate for bis-protonation with the highest pK, (MeCN) value of 50.1 to date. The side phenyl ring in paracyclophane systems that is not directly involved in C-H~+···π type interactions contributes to augment the basicity by through-space π-π interactions. The side ring of the paracyclophane system is involved in enhancement of the proton affinity of 19.3 kj/mol via through-space π-π interaction. Molecular electrostatic potential (MESP) analysis shows that such noncovalent interactions can enhance the electron density at the reactive sites in suitably designed systems. The absolute minima of the MESP (V_(min)) located for these carbene systems correlate well with their calculated proton affinity values. The frontier molecular orbital energy differences (HOMO-LUMO) of such carbenes also correlate well with their proton affinity results. These paracyclophane-based carbene systems can be used for selective binding of lithium ions. Such lithium decorated systems can be exploited as a molecular container for the storage of multiple dihydrogen. This is the first example of the use of lithiated organic superbases as hydrogen storage material. The calculated conceptual density functional theory-based reactivity descriptors such as electronegativity, hardness, and electrophilicity indicate the stability of these H2 trapped molecules. The calculated desorption energies per H2 molecule (ΔE_(DE)) also indicate the recyclable property of the hydrogen storage materials.