Synthetic and structural investigations of bis(N-alkyl-benzoselenadiazolium) cations.

The synthesis, and spectroscopic and structural characterization of bridged dicationic derivatives of benzo-2,1,3-selenadiazoles are reported. The chloride salt of [H4C6NSeN-CH2-CH2-NSeNC6H4](2+) crystallizes forming a macrocyclic structure in which two cations are bridged by SeMIDLINE HORIZONTAL ELLIPSISCl chalcogen bonds (ChBs), with a third chloride at the centre of the macrocycle. The structure of [1,2-(H4C6NSeN)(2)-C6H10]Cl-2 consists of two selenadiazolium cations linked by a chiral cyclohexane and capped by SeMIDLINE HORIZONTAL ELLIPSISCl ChBs. Tetrafluoroborate salts of a xylene bridge crystallize in two pseudopolymorphs in which the cations form SeMIDLINE HORIZONTAL ELLIPSISF ChBs in an anti- or syn-conformation. The triflate salt of ethylene-bridged cations dimerizes through the formation of the [Se-N](2) supramolecular synthon with SeMIDLINE HORIZONTAL ELLIPSISO ChBs capping the second selenium atom. In contrast, [H4C6NSeN-CH2-CH2-CH2-NSeNC6H4](CF3SO3)(2) only forms SeMIDLINE HORIZONTAL ELLIPSISO ChBs.