Structures and spectral properties of 5-phenyl-5H-benzo[b]phosphindole 5-oxide and its substituted derivatives: The substitutional effect study based on density functional theory calculations.

• Different electronic donating/accepting groups (Na, MP, MB, BN) were introduced onto the C8 position of 5-phenyl-5H-benzo[ b ]phosphindole 5-oxide(PhBPO). • Substitution effect on the structure and spectral properties was revealed according to density functional theory (DFT) calculation. • ground state geometries, orbital energy gaps, infrared (IR) spectra, UV–vis spectra, and fluorescence spectra of these PhBPO derivatives were described systematically. • These compounds possess easy-to-modify sites and are good candidates as potential functional building block. • These compounds are good fluorescence materials and substitution helps increase the fluorescence strength. The properties of phosphole-based π-conjugated compounds could be well tuned via simple chemical modification. Four π-conjugated groups with different electronic nature including naphthalen-2-yl, 4-methoxyphenyl, 4-Methyl benzoate, and 4-benzonitrile were introduced to the C8 position of 5-phenylbenzo[ b ]phosphindole 5-oxide (PhBPO) to reveal the relationship between structures and properties. Density functional theory (DFT) calculations were carried out to comparatively study the ground state geometries, orbital energy gaps, infrared (IR) spectra, UV–vis spectra, and fluorescence (FL) spectra of the five PhBPO derivatives. Good correspondences between the simulated and experimental IR and UV–vis spectral properties were found, proving the feasibility of the DFT method. The IR and Uv-vis spectra were assigned and explained in detail on the basis of the calculation results and the substituional effect of different substituents on the structure and spectral properties was revealed. The large FL oscillator strengths indicate these PhBPO derivatives are good candidates for fluorescent materials. PhBPO derivatives possess easy-to-modify sites and thus can be further utilized as functional materials. Image, graphical abstract [ABSTRACT FROM AUTHOR]