Modulation of Solid-State Optical Properties of <i>o</i>-Hydroxynaphthoic Acids through Formation of Charge Transfer Cocrystals with TCNB
Qianqian Hao, Xia-Lin Dai, Yong‐Liang Huang, Jia‐Mei Chen, Tong‐Bu Lu
Abstract
Charge transfer cocrystals offer an opportunity to alter the photophysical characteristics of organic chromophores in the solid state. A set of new charge transfer cocrystals of three positional isomers of o-hydroxynaphthoic acid with 1,2,4,5-tetracyanobenzene (TCNB) as the electron acceptor was prepared and subjected to single-crystal and powder X-ray diffraction, thermal analysis, vibrational, and UV–vis absorption and fluorescence spectroscopic measurements. Crystal structure analyses reveal that the donor and acceptor molecules are combined in a 2:1 stoichiometric ratio and stacked alternately through a typical mixed face-to-face arrangement (DAD···DAD), forming a columnlike charge transfer structure involving π-stacking interactions. All of the cocrystals exhibit distinct tunable emission colors and photoluminescence characteristics due to the charge transfer transition states. This research indicates that the cocrystal strategy can be applied to effectively modulate the optical properties of o-hydroxynaphthoic acid compounds, which have a great research value in optoelectronic applications.