Unveiling fluorescence sensing ability of two newly synthesized near-infrared emitting dicyanoisophorone derivatives.

In this manuscript, two newly designed near-infrared (NIR) emitting derivatives were synthesized by reacting dicyanoisophorone with 2-hydroxy-5-nitrobenzaldehyde (IC25) and 2,4,5-trimethoxybenzaldehyde (IC27) through Knoevenagel condensation reactions. The compounds were structurally characterized using various analytical techniques and single-crystal X-ray diffraction (SC-XRD). Following the twisted intramolecular charge transfer (TICT) mechanism, the derivatives IC25 and IC27 were employed for the detection of human serum albumin (HSA) and viscosity. Upon interaction with HSA, IC25 exhibited a distinct red fluorescence under UV365nm light irradiation, accompanied by strong fluorescence enhancement at 635 nm. The probe IC25 demonstrated high sensitivity, excellent selectivity and rapid response towards HSA over other examined bioactive analytes. The detection of HSA by IC25 was supported by both experimental and theoretical studies, and its practical applicability was validated in real biological samples. Further studies revealed that IC27 showed significant fluorescence enhancement upon a change in viscosity because of the TICT phenomenon.