Photophysical properties of 3-[2-(N-phenylcarbazolyl)benzoxazol-5-yl]alanine derivatives—experimental and theoretical studies

Abstract

Solvatochromic probes are often used in biophysical studies to obtain information about polarity of the microenvironment. As there is not much natural fluorophores with such properties, there is still need for new synthetic compounds such as 3-(2-benzoxazol-5-yl)alanine derivatives. Among this group of non-proteinogenic fluorescent amino acids especially interesting are 3-[2-(4-aminophenyl)benzoxazol-5-yl]alanine derivatives whose solvatochromism depends on the substituents on the nitrogen atom, as revealed by our recent studies. To expand them we synthesized two new derivatives with an N-phenylcarbazole moiety in position 2 of the benzoxazole ring and studied their photophysical properties in solvents of different polarity and ability to form hydrogen bonds using absorption and steady-state and time-resolved fluorescence spectroscopy. Applying single parameter and multi-linear correlations with different solvent parameters, the excited state dipole moments were determined as well as the influence of solvent parameters on each photophysical property was estimated. Moreover, the geometry of compounds and vertical absorption transition were theoretically calculated (DFT and TD DFT methods). It was found that the place of substitution of the N-phenylcarbazole part by the benzoxazole unit determines the character of the electron transition (π-π* or ICT) and thereby the spectral and photophysical properties of the compounds studied.

Solvatochromic studies of pull–push molecules containing dimethylaniline and aromatic hydrocarbon linked by an acetylene unit

“…It is also frequently used as a parameter of linear solvation energy relationships for the correlation analysis of solvent effect on chemical and physical properties. [18][19][20][21][22] For non-hydrogen bond donor solvents, E T (30) or E T N parameter describes almost exclusively the electrostatic forces between solute and solvent. 23 Apart from the dependence of different spectral and photophysical properties on E T N parameter, the correlation of the Stokes shi with this parameter can be applied to calculate the dipole moment change between the excited and ground state based on the equation proposed by Ravi et al: 24,25 Dñ ¼ ña À ñf ¼ 11307:6…”

Synthesis and Spectral Properties of a Novel Fluorescent Probe for Zn2+ Based on a Benzoxazole Fluorophore

“…Benzoxazole is widely used as a fluorophore for synthesising fluorescence probes to detect metal ions on account of its good photophysical and photochemical properties. [16][17][18] A novel benzoxazole-derived fluorescent probe 2 was synthesised via the Schiff-base condensation reaction, as illustrated in Scheme 1. It was identified on the basis of IR, NMR, MS and elemental analysis, and its metal-binding properties towards Zn 2+ were investigated by spectrometry.…”

Effect of solvent polarity on the photophysical properties of chalcone derivatives

“…The multiple linear regression analyses proposed by Kamlet-Abboud-Ta 59 and Catalan 60 have been used to correlate absorption maxima, emission maxima and Stokes shi energies. [61][62][63]…”