Time-dependent density functional theory calculations of the solvatochromism of some azo sulfonamide fluorochromes.

Przemysław Krawczyk

doi:10.1007/s00894-015-2651-z

Abstract

The absorption and emission spectra of three azo sulfonamide compounds in different solvents were investigated theoretically by using response functions combined with density functional theory (DFT), while the solvent effect on the structure and the electronic transitions was determined using the integral equation formalism for the polarizable continuum model (IEF-PCM). The results show that the applied different exchange-correlation functionals can reproduce the experimental values well. DFT calculations of the title compounds showed that the H-bond formed between the solute and solvent molecules is one of the major causes of the reversible solvatochromism observed in measured spectra. This is due to a better stabilization of the neutral form than the zwitterionic form in the polar protic solvents, which is characteristic of the hypsochromic shift. On the other hand, the molecules considered exhibit a monotonic behavior regarding the polarity of the low-lying excited state (Δμg–CT) as a function of the solvent polarity. This dependence occurs in the case of the positive solvatochromism and confirms the thesis regarding the H-bond solute–solvent interactions. Theoretically determined values of the two-photon cross section revealed that the (σOF(2)) shows similar trends with changes in λabs, in contrast to 〈δOF〉 values. In conclusion, the results demonstrate that the investigated molecules can be used successfully as fluorochromes in bioimaging.Electronic supplementary materialThe online version of this article (doi:10.1007/s00894-015-2651-z) contains supplementary material, which is available to authorized users.

Highlights

The pharmacological activities of sulfonamide derivates have been well known for many years [1]
The results show that the tested azo sulfonamides, as a group of the D-π-A chromophores, are characterized by the existence of excited states with large differences in polarity between the electronic excited state and the ground state (Δμg-CT)
The results obtained during TD-density functional theory (DFT) calculations are in good agreement with the experimental absorption and emission spectra and the most reliable values are obtained for the PBE0 functional

Summary

Introduction

The pharmacological activities of sulfonamide derivates have been well known for many years [1]. In addition to continuing research on antibacterial activity, and on hypoglycemic and diuretic sulfonamides [2,3,4,5,6,7], this interest is related to other biological activities and is strictly dependent on structure. The literature cites sulfonamides as selective COX-2 inhibitors, bradykinin B2 receptor antagonists, receptor selective antagonists of 5-HT7, receptor selective antagonists endothelin ETA, receptor ligands serotonin 5-HT6 or selective inhibitors of bacterial collagenase. Most of these reports are related to studies on the synthesis of new sulfonamides and their effect on cancer or HIV. In 1996 studies began on 5,5,11-trioxo-10Hpyrrolo[1,2 -b] [1, 2, 5] benzothiadiazepine (PBTDs), 1-(benzenesulfonyl)-1H-pyrrole and 1-(benzenesulfonyl)1H-indole [12, 13] with activity directed against HIV-1

Methods

Results

Conclusion