Conformational Analysis of Dibutylphosphorylacetic Acid N,N-Dibutylamide in Solution

Structure of Tris[2-(4-pyridyl)ethyl]phosphine, Tris[2-(2-pyridyl)ethyl]phosphine, and Their Chalcogenides in Solution: Dipole Moments, IR Spectroscopy, and DFT Study

“…The combination of experimental methods, especially dipole moments, with DFT calculations, including using the CPSM model, made it possible to identify the general regularities of the conformational flexibility of the studied compounds with many axes of internal rotation in solution. Thus, the conformations of their molecules fit into the overall conformational picture for compounds of tri- and tetra-coordinated phosphorus with the phosphorus–chalcogen bonds and arylalkyl substituents at the phosphorus atom [ 52 , 53 , 54 , 55 ]. It was found that, in solution, compounds 1 – 8 exist as an equilibrium of mainly non-eclipsed ( synclinal or antiperiplanar ) forms, with a predominance of the symmetrical conformer having a gauche -orientation of the C sp3 –C sp3 bonds of pyridylethyl substituents relative to the P=X bond (X = LP, O, S, Se) and a gauche -orientation of the pyridyl rings relative to the zigzag ethylene bridges.…”

“…Then, we performed the calculations in the extended basis set 6-311++G(df,p) and selected the preferred conformers with relative energies less than 7.6 kJ/mol while removing mirror isomers with the same dipole moments and relative energies. Next, refinement calculations were carried out for the preferred conformers in solution using the CPCM model, which takes into account the influence of the solvent and gives more accurate values of the dipole moments [ 52 , 54 ]. The percentage of conformers was calculated from the Gibbs free energies.…”

“…The method of dipole moments is a high-precision instrument for the conformational analysis of polar compounds in solution, and it is successfully used in combination with other physical methods and quantum chemistry to study the fine features of the spatial and electronic structure of organic and organoelement compounds [52,54,56].…”

“…Equations for α and γ calculations (Guggenheim-Smith equation) as well as the εi-wi and ni 2 -wi plots (Figures S1-S3, Table S1) are given in the Supplementary Materials. The method of dipole moments is a high-precision instrument for the conformational analysis of polar compounds in solution, and it is successfully used in combination with other physical methods and quantum chemistry to study the fine features of the spatial and electronic structure of organic and organoelement compounds [52,54,56].…”

“…Previously, we studied the structure in solution of a vast array of compounds of three- and four-coordinated phosphorus with multiple phosphorus–chalcogen bonds (chalcogen–oxygen, sulfur, selenium) and alkyl, aryl, and hetaryl substituents: tris(2-pyridyl)phosphine and its chalcogenides [ 41 ], Se -esters of diselenophosphinic acids [ 52 ], tri(1-naphthyl)phosphine, tri(2-naphthyl)phosphine, and their chalcogenides [ 53 ], and N , N -dibutylamide of dibutylphosphorylacetic acid [ 54 ]. A conformational analysis of these compounds was carried out using the methods of dipole moments, IR spectroscopy, and quantum chemistry B3PW91/6-311++G(df,p).…”