4 research outputs found
MOLECULAR INTERACTION BETWEEN BENZONITRILEAND HEXAMETHYLPHOSPHORIC TRIAMIDEBY 13CNMR T1RELAXATIONTIME STUDIES ANDAS INITIOQM CALCULATIONS: EXTENDED INVESTIGATION
ABSTRACT
It has been obtained the anisotropy ratio a = Tdortho-,meta-13C)/Tdpara-13Co)f dilute solutions of bn change
from 1.7 in fa solution and 1.5 in neat bn to 1.0 in HMPT. Thus the anisotropyratio comes out to be a = 1. In HMPT,
obviously, solvent molecules cluster around Ph-C=N in such a way, that non-covalent interactions lead to isotropic
reorientational motion like a spherical molecule. To conform with the T1times, a layer arrangement with at least two
HMPT molecules per Ph-C=N seems to be likely. From computational quantum calculations of non-covalent
intermolecular interactions and Mie potential analysis, the solute-solventmolecularpairs in bn.. .HMPThave almost
equal interaction energies for the ortho, meta, and para configuration and the layered configurations are
energeticallypermitted
Keywords: 13CT1spin-lattice relaxation times, ab initio quantum chemistry calculations, intermolecular interactions,
isotropic and anisotropic rotational motio
A new apodization function for resolution enhancement with a minimum loss of sensitivity
MOLECULAR INTERACTION BETWEEN BENZONITRILE AND HEXAMETHYLPHOSPHORIC TRIAMIDE BY <sup>13</sup>C NMR T<sub>1</sub> RELAXATION TIME STUDIES AND AB INITIO QM CALCULATIONS: EXTENDED INVESTIGATION
It has been obtained the anisotropy ratio a = T1(ortho-,meta-13C)/T1(para-13C) of dilute solutions of bn change from 1.7 in fa solution and 1.5 in neat bn to 1.0 in HMPT. Thus the anisotropy ratio comes out to be a = 1. In HMPT, obviously, solvent molecules cluster around Ph-CÂșN in such a way, that non-covalent interactions lead to isotropic reorientational motion like a spherical molecule. To conform with the T1 times, a layer arrangement with at least two HMPT molecules per Ph-CÂșN seems to be likely. From computational quantum calculations of non-covalent intermolecular interactions and Mie potential analysis, the solute-solvent molecular pairs in bn֌֌֌HMPT have almost equal interaction energies for the ortho, meta, and para configuration and the layered configurations are energetically permittedÂ
Â
Keywords: 13C T1 spin-lattice relaxation times, ab initio quantum chemistry calculations, intermolecular interactions, isotropic and anisotropic rotational motio
INVESTIGATION OF MOLECULAR INTERACTION BETWEEN PHENYLACETYLENE AND HEXAMETHYLPHOSPHORIC TRIAMIDE BY <sup>13</sup>C NMR T<sub>1</sub> RELAXATION TIME STUDIES AND AB INITIO QM CALCULATIONS
Intermolecular interactions and molecular translational and rotational mobility are key factors in molecular material sciences, e.g. liquid crystals. One of the important substructures is given by phenylacetylene, Ph-CÂșCH. Its rotational behavior in its pure form and in high dilution in hexamethylphosphoric triamide OP[N(CH3)2]3 (HMPA) has been studied by means 13C NMR T1 relaxation times at ambient temperature as measured by the inversion recovery method. HMPA is an exceptional solvent in that is has a quite large dipole moment but comparatively low relative dielectricity constant. From the molecular shape Ph-CÂșCH is expected to exhibit anisotropic rotational diffusion which in fact can be deduced from the measured set of T1 values of the ortho, meta and para carbon nuclei in the neat liquid as well as in the HMPA solution. This expected result rules the dominance of a linearly molecules pair Ph-CÂșCH...HMPA along their dipole moment axes as anticipated in view of the large HMPA dipole moment. In order to conform with the T1 data, a linear arrangement of Ph-CÂșCH via the interaction between its weakly acidic H-atom with negatively charge O-atom of HMPA molecules seems to lead to such an anisotropic rotational motion. This hypothesis is supported by ab initio QM calculations which come out with higher interaction energy for linear orientation than other geometries. These ab initio calculations were performed with the basis set of RHF/6-31G(d) for the single molecules of Ph-CÂșCH and HMPA as well as for their various geometries of the molecules pair. Molecular dynamics simulations need to be performed for further confirmation.
Â
Keywords: Relaxation Times, HMPA, pheylacetylene, ab initio, intermolecular interaction, rotational diffusio