Stepwise coordination isomerism of 2D networks: adsorption of diiodomethane into crystals and recognition in SCSC mode

Abstract

Reaction of CdI₂ with C₂-symmetric multidentate N-donor (L) in a mixture of ethanol and dichloromethane produces single crystals of 3(dichloromethane)·2(ethanol)@[CdI₂L] (23.26 Å thickness layer) with a new 2D topology of {4³·6²·8}. These single crystals in tetrahydrofuran are isomerized into new single crystals of 4(tetrahydrofuran)@[CdI₂L] (9.15 Å thickness layer) with a 2D topology of sql {4⁴·6²}. The tetrahydrofuran solvate molecules of 4(tetrahydrofuran)[CdI₂L] are fully replaced by adsorption of dihalomethane molecules in the single-crystal-to-single-crystal (SCSC) mode. The most interesting feature is that both 3(dichloromethane)·2(ethanol)@[CdI₂L] and 4(tetrahydrofuran)@[CdI₂L] crystals are integral to an efficient and tolerant matrix for recognition of diiodomethane (CH₂I₂) in the SCSC mode, even though the adsorption rate of 4(tetrahydrofuran)@[CdI₂L] crystals is much faster than that of 3(dichloromethane)·2(ethanol)@[CdI₂L]. That is, their blue photoluminescence is significantly quenched in the presence of diiodomethane, and recovered by removal of the diiodomethane.