mPW1PW91 Calculated Structures and IR Spectra of the Conformational Stereoisomers of C-Cyanophenyl Pyrogallol[4]arene

Abstract

Molecular structures of the various conformational stereoisomers of 2,8,14,20-cyanophenyl pyrogallol[4]arenes 1 were optimized using the mPW1PW91 (hybrid Hartree-Fock density functional) calculation method. The total electronic and Gibbs free energies and the normal vibrational frequencies of the different structures from three major conformations (CHAIR, TABLE, and 1,2-Alternate) of the four stereoisomers [1(rccc), 1(rcct), 1(rctt), and 1(rtct)] were analyzed. The mPW1PW91/6-31G(d,p) calculations suggested that 1(rcct) 1,2-A , 1(rctt) CHAIR , and 1(rtct) CHAIR were the more stable conformations of the respective stereoisomers. Hydrogen bonding is the primary factor for the relative stabilities of the various conformational isomers, and maximizing the π-π interaction between the cyanophenyl rings is the secondary factor. The calculated IR spectra of the more stable conformers [1(rctt) CHAIR , 1(rcct) 1,2-A , 1(rtct) CHAIR ] were compared with the experimental IR spectrum of 1(rctt) CHAIR .

Synthesis and Crystal Structure of a Ternary Lattice Inclusion System of C‐4‐acetamidophenylcalix[4]‐2‐methylresorcinarene dimethylsulfoxide tetrasolvate dihydrate

“…The instability of the compounds can be observed not only when exposed to air but even after keeping it for some times in solution. It is now known that the flexibility of the conformers, formation and number of hydrogen bonds between the calix molecule and the solvent molecules strongly influence the stability of the conformation . On the other hand the presence of many solvent molecules could pose a problem in locating the hydrogen atoms and disordered behavior in chemical crystallography studies even with data collected at low temperatures.…”