Molecular Recognition by Chalcogen Bond: Selective Charge?Transfer Crystal Formation of Dimethylnaphthalene with Selenadiazolotetracyanonaphthoquinodimethane

The title nonplanar electron acceptor (1) fused with a selenadiazole ring selectively forms crystalline charge-transfer complex (CT crystal) 2,6-dimethylnaphthalene (2,6-DMN). On the other hand, sulfur analogue (2) has less recognition ability and CT crystals both 2,6- 2,7-DMN. X-ray analyses of 1, 2, their revealed that Se???N chalcogen bond (ChB) in 1 is strong enough to determine crystal packing formation cavity suitable for 2,6-DMN. contrary, ChB through S???N contact 2 competes weak interactions such as C?H???N hydrogen bond. stronger involving Se key separate 2,6-DMN (>97 wt %) from isomer mixture containing ca. 10 % each 2,7-DMN by simple, efficient straightforward mixing-filtration-heating process.