Premium
Photophysical Properties of Fluorescent 2‐(Phenylamino)‐1,10‐phenanthroline Derivatives †
Author(s) -
Teixeira Rodolfo I.,
Silva Ramon B.,
Gaspar Caio S.,
Lucas Nanci C.,
Garden Simon J.
Publication year - 2020
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.13303
Subject(s) - bathochromic shift , hypsochromic shift , substituent , chemistry , photochemistry , excited state , fluorescence , homo/lumo , blueshift , emission spectrum , polar effect , absorption (acoustics) , absorption spectroscopy , spectral line , photoluminescence , stereochemistry , materials science , molecule , atomic physics , organic chemistry , physics , optoelectronics , quantum mechanics , astronomy , composite material
The present study details the experimental and theoretical characterization of the photophysical properties of 14 examples of 2‐(phenylamino)‐1,10‐phenanthrolines ( 1 ). The absorption spectra of 1 are substituent‐dependent but in a general manner present absorption bands at wavelengths of ~230; ~300; ~335 and a shoulder at ~380 nm. Electron‐donating groups (EDG) and electron‐withdrawing groups (EWG), respectively, result in bathochromic and hypsochromic shifts. Compounds 1 are highly luminescent, in contrast to phenanthroline, and emit in the region between 350 and 500 nm with substituent‐dependent λ max emission. The emission spectra show a redshift for EDG (4‐OMe 62 nm; 4‐Me 19 nm) and a blueshift for EWG (4‐CN 41 nm; 4‐CF 3 38 nm) relative to the emission of the unsubstituted parent compound 1a . Plotting the λ max EM against Hammett σ+ constants gave an excellent linear correlation demonstrating the electron‐deficient nature of the excited state and how the substituents (de)stabilize S 1 . Theoretical calculations revealed a HOMO‐LUMO π‐π* electronic transition to S 1 which in combination with difference (S 1 –S 0 ) in electron density maps revealed charge‐transfer character. Strongly electron‐withdrawing substituents switch off the charge transfer to give rise to a local excitation.