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Vibrational solvatochromism of nitrile infrared probes: beyond the vibrational Stark dipole approach
Błasiak, Bartosz,Ritchie, Andrew W.,Webb, Lauren J.,Cho, Minhaeng The Royal Society of Chemistry 2016 Physical chemistry chemical physics Vol.18 No.27
<P>Systematic probing of local environments around biopolymers is important for understanding their functions. Therefore, there has been growing interest in in situ measurements of molecular granularity and heterogeneity through the systematic analysis of vibrational frequency shifts of carbonyl and nitrile infrared probes by vibrational Stark dipole theory. However, here we show that the nitrile vibrational frequency shift induced by its interaction with the surrounding molecules cannot be solely described by electric field-based theory because of the exchange-repulsion and dispersion interaction contributions. Considering a variety of molecular environments ranging from bulk solutions to protein environments, we explore the distinct scenarios of solute-environment contacts and their traces in vibrational frequency shifts. We believe that the present work could provide a set of clues that could be potentially used to design a rigorous theoretical model linking vibrational solvatochromism and molecular topology in complex heterogeneous environments.</P>
Błasiak, Bartosz,Londergan, Casey H.,Webb, Lauren J.,Cho, Minhaeng American Chemical Society 2017 Accounts of chemical research Vol.50 No.4
<P>Over the past few years, we have developed a systematic approach to simulating vibrational solvatochromic data based on the effective fragment potential approach, one of the most accurate and rigorous theories on intermolecular interactions. We have further elucidated the interplay of local electric field with the general vibrational solvatochromism of small IR probes in either solvents or complicated biological systems, with emphasis on contributions from non-Coulombic intermolecular interactions to vibrational frequency shifts and fluctuations. With its rigorous foundation and close relation to quantitative interpretation of experimental data, this and related theoretical approaches and experiments will be of use in studying and quantifying the structure and dynamics of biomolecules with unprecedented time and spatial resolution when combined with time-resolved vibrational spectroscopy and chemically sensitive vibrational imaging techniques.</P>
Distributed Multipolar Expansion Approach to Calculation of Excitation Energy Transfer Couplings
Błasiak, Bartosz,Maj, Michał,Cho, Minhaeng,Gó,ra, Robert W. American Chemical Society 2015 Journal of chemical theory and computation Vol.11 No.7
<P>We propose a new approach for estimating the electrostatic part of the excitation energy transfer (EET) coupling between electronically excited chromophores based on the transition density-derived cumulative atomic multipole moments (TrCAMM). In this approach, the transition potential of a chromophore is expressed in terms of truncated distributed multipolar expansion and analytical formulas for the TrCAMMs are derived. The accuracy and computational feasibility of the proposed approach is tested against the exact Coulombic couplings, and various multipole expansion truncation schemes are analyzed. The results of preliminary calculations show that the TrCAMM approach is capable of reproducing the exact Coulombic EET couplings accurately and efficiently and is superior to other widely used schemes: the transition charges from electrostatic potential (TrESP) and the transition density cube (TDC) method.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jctcce/2015/jctcce.2015.11.issue-7/acs.jctc.5b00216/production/images/medium/ct-2015-00216f_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ct5b00216'>ACS Electronic Supporting Info</A></P>