Density Functional Study on the Adsorption of 5‑Membered N‑Heterocycles on B/N/BN-Doped Graphene: Coronene as a Model System

Adsorption of seven 5-membered N-heterocycles on B/N/BN-doped graphene (with coronene as a model system) has been studied using density functional theory (DFT). The geometry of the complexes validated the involvement of both π···π stacking and N–H···π interaction in the adsorption process. The stability of the complexes is measured in terms of stabilization energy, and the results suggested that the complexes are stable enough (stabilization energies are in the range of 7.61–14.77 kcal mol–1). Studies confirmed the stability of complexes in the solvent phase too irrespective of the dielectric of the solvent. Dispersive force is the major mode of interaction in stabilizing the complexes. Natural bond orbital analysis indicated a small contribution from electrostatic and covalent interactions. Thermochemical analysis revealed that the complexation is exothermic in nature and favorable at a lower temperature. Adsorption of N-heterocycles exerts a nominal impact on the electronic properties of the undoped/doped graphene. The study presents a simple approach to introduce an arbitrary functionality to undoped/doped graphene by preserving its electronic properties

Adsorption of Dilute Alcohols onto Cyclodextrin–Polysulfone Membrane: Experimental and Theoretical Analysis

The adsorptive separation of dilute alcohols onto polymeric membrane has been investigated in this work. The adsorption experiments have been performed in a stirred reactor using an indigenously developed membrane. Equilibrium adsorption isotherms and kinetics have also been investigated. The kinetic data experimentally obtained at different concentrations have been analyzed using pseudo-first-order, pseudo-second-order, and an intraparticle diffusion models. The experimental data satisfied the pseudo-second-order model well. Adsorption isotherms have been interpreted from Langmuir, Freundlich, and Temkin isotherms, and Langmuir isotherm exhibited a better fit to the experimental data. It has been observed that the adsorption depends on the different interactions occurring at the solid–liquid interface, i.e., hydrophobic, dipole–dipole, and hydrogen bonding which are interpreted by considering interaction energy between adsorbent and adsorbate using density functional theory and MP2. Physical properties of the adsorbent and quantitative structure–activity relationship properties of the adsorbate play an important role in the equilibrium of adsorption. The experimental value of heat of adsorption (Δ<i>H</i>⁰) has been determined from the van’t Hoff plot using equilibrium data at different temperatures

Substituent and Solvent Effects on the Absorption Spectra of Cation−π Complexes of Benzene and Borazine: A Theoretical Study

Time-dependent density functional theory (TDDFT) has been used to predict the absorption spectra of cation−π complexes of benzene and borazine. Both polarized continuum model (PCM) and discrete solvation model (DSM) and a combined effect of PCM and DSM on the absorption spectra have been elucidated. With decrease in size of the cation, the π → π* transitions of benzene and borazine are found to undergo blue and red shift, respectively. A number of different substituents (both electron-withdrawing and electron-donating) and a range of solvents (nonpolar to polar) have been considered to understand the effect of substituent and solvents on the absorption spectra of the cation−π complexes of benzene and borazine. Red shift in the absorption spectra of benzene cation−π complexes are observed with both electron-donating groups (EDGs) and electron-withdrawing groups (EWGs). The same trend has not been observed in the case of substituted borazine cation−π complexes. The wavelength of the electronic transitions corresponding to cation−π complexes correlates well with the Hammet constants (σ_p and σ_m). This correlation indicates that the shifting of spectral lines of the cation−π complexes on substitution is due to both resonance and inductive effect. On incorporation of solvent phases, significant red or blue shifting in the absorption spectra of the complexes has been observed. Kamlet–Taft multiparametric equation has been used to explain the effect of solvent on the absorption spectra of complexes. Polarity and polarizability are observed to play an important role in the solvatochromism of the cation−π complexes