Experimental Insights into the Electronic Nature, Spectral Features, and Role of Entropy in Short CH3 center dot center dot center dot CH3 Hydrophobic Interactions

Sarkar, Sounak and Thomas, Sajesh P and Potnuru, Lokeswara Rao and Edwards, Alison J and Grosjean, Arnaud and Ramanathan, Krishna Venkatachala and Row, T N Guru (2019) Experimental Insights into the Electronic Nature, Spectral Features, and Role of Entropy in Short CH3 center dot center dot center dot CH3 Hydrophobic Interactions. In: JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 10 (22). pp. 7224-7229.

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Abstract

Hydrophobic interactions are often explored in solution-state aggregation of molecules. However, an experimental electron density description about these interactions is still lacking. Here, we report a systematic study on the electronic nature of methyl center dot center dot center dot methyl hydrophobic interactions in a series of multicomponent crystals of biologically active molecules. Charge density models based on high-resolution X-ray diffraction allow the visualization of subtle details of electron density features in the interaction region. Our study classifies these interactions as atypical group center dot center dot center dot group interactions in contrast to sigma-hole interactions, which are stabilized by the minimized electrostatic repulsion and maximized dispersion forces. For the first time, we quantified the solid-state entropic contribution from the torsional mode of the methyl groups in stabilizing these interactions by thermal motion analysis based on neutron diffraction as well as variable-temperature crystallography. The carbon atoms in methyl center dot center dot center dot methyl interactions show a unique upfield chemical shift in the C-13 solid-state NMR signal.

Item Type:	Journal Article
Publication:	JOURNAL OF PHYSICAL CHEMISTRY LETTERS
Publisher:	AMER CHEMICAL SOC
Additional Information:	Copyright of this article belongs to AMER CHEMICAL SOC
Keywords:	CHARGE-DENSITY ANALYSIS; INTERMOLECULAR INTERACTIONS; SOLID-STATE; ACCURATE; ENERGIES
Department/Centre:	Division of Chemical Sciences > NMR Research Centre (Formerly Sophisticated Instruments Facility) Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	17 Dec 2019 05:44
Last Modified:	17 Dec 2019 05:44
URI:	http://eprints.iisc.ac.in/id/eprint/64048

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