Nonlinear optical response and two-photon biological applications of a new family of imidazole-pyrimidine derivatives

• A series of novel imidazole-pyrimidine derivatives (EX-1∼EX-4) were designed and confirmed by crystallography.
• The photophysical properties were systematically investigated.
• The 2PA cross-section values (σ) were obtained both by Z-Scan and 2PEF measurements.
• EX-1 and EX-2 were identified to be the best candidates for living cells (HepG2) imaging.

A series of novel D–π–A type two-photon absorption (2PA) imidazole-pyrimidine derivatives (EX-1∼EX-4) have been synthesized and characterized, with EX-1 was crystallography confirmed. Based on systematic photophysical investigations, the structure–property relationships can be drawn as follows: (1) Both theoretical and experimental studies indicated that the different donor groups have large influences on the optical properties. (2) The 2PA cross-section values (σ) were obtained both by Z-Scan and two-photon excited fluorescence (2PEF) measurements. 2PA cross sections show an increasing trend with increasing electron-donating strength and the number of branches. (3) Comprehensively considered the optical performance, molecular volume, cytotoxicity and solubility, EX-1 and EX-2 were identified to be the best candidates for living cells (HepG2) imaging. Moreover, the 2PA excitable features of EX-1 and EX-2 are capable of imaging in fresh mouse's liver tissues with a depth of ca. 70 μm.

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