Theoretical study on cyclophane amide molecular receptors and its complexation behavior with TCNQ.

Complexation behavior of cyclophane amide molecular receptors towards 7,7,8,8-tetracyanoquinodimethane (TCNQ) studied. TD-B3LYP/6-31 + G(d,p) based density functional theory was employed to investigate the photophysical characteristics of the complexes obtained. Syn isomers of cyclophane amide molecular hosts show preferred conformation over other conformations. Molecular Orbital analysis indicates the electronic structure change, which reflects in the absorption spectra of the cyclophane amide-1@TCNQ, and cyclophane amide-2@TCNQ charge-transfer (CT) complexes. Binding energy studies with B3LYP-D3/6-31 + G (d,p) theory demonstrated that the more effective binding of the pyridine-2,6-dicarboxamide macrocycles than for their isophthalamide analogs. Both the CT complexes show intermolecular bifurcated hydrogen bonding (N-H(host)···N(guest)···H-N(host)) interactions (2.06 to 2.08 Å), and π(host)···π(guest) interactions (3.2 to 3.4 Å). Calculated BSSE corrected complexation energy (ΔE) be associated with the formation of the inclusion complexes in the range - 28 to -37 kJ mol-1, indicating spontaneity of host-guest complex formation in both the cases. From the calculated vibrational spectra of these complexes, the formation of inclusion complexes via N - H(host)···N(guest) and π(host)···π(guest) intermolecular interactions established by the frequency shift in the N - H vibrations. Mulliken population analysis performed to recognize the CT process and the variation in charges between the free and complex TCNQ molecules suggests the intermolecular charge transfer. This study indicates that these cyclophane amides can be a decent CT complexation host for the guests like TCNQ.

Metal-free boron-doped graphene for selective electroreduction of carbon dioxide to formic acid/formate.

Herein we report the electrocatalytic activity of boron-doped graphene for the reduction of CO2. Electrolysis takes place at low overpotentials leading exclusively to formate as the product (vis-à-vis benchmark Bi catalyst). Computational studies reveal mechanistic details of CO2 adsorption and subsequent conversion to formic acid/formate.