Remarkable Self-Assembly of Salicylideneimine-Boron Complexes into Plastic Crystals and Organogels

Abstract

Salicylideneimine-boron complexes are known to exhibit interesting photophysical properties, but fine-tuning their luminescence and mechanical properties through side-chain engineering is hitherto unknown. We report two salicylideneimine-boron complexes, the self-assembly and photophysical properties of which are reliant on the side chains: an alkyl chain imparted plasticity to the single crystals, while a fluoroalkyl chain facilitated gelation. The flexible crystals of the compound containing the alkyl chain displayed optical waveguide properties, whereas the fluorous molecule was employed for white light emission and hydrophobic luminescent marker applications. Crystallography and NMR studies indicated that weak C−H•••F and B−F•••π interactions are the key in defining the distinctive self-assembly behavior of these compounds.

Advances in the Supramolecular Chemistry of Tetracoordinate Boron-Containing Organic Molecules into Organogels and Mesogens

“…Reproduced with permission from Sun et al, 2018Sun et al, , copyright 2018 Royal Society of Chemistry. Reproduced from Naim et al, 2021, copyright 2021 American Chemical Society. Reproduced from Wong et al, 2017Wong et al, , copyright 2017 American Chemical Society.…”

“…Reproduced with permission from Wu et al, 2017, copyright 2017 between methyl groups and the neighboring molecules were ascertained to be the driving forces for gelation. Our group recently showed that the chemical composition of the sidechain has a significant influence on the self-assembly as well as the mechanical and luminescent properties of boron difluoride complexes (Naim et al, 2021). While complex 4a with an alkyl chain formed plastic crystals whereas the complex 4b with a fluoroalkyl chain favored the formation of organogels.…”

Luminescent hexagonal microtubes prepared through water-induced self-assembly of a polymorphic organoboron compound: formation mechanism and waveguide behaviour

“…[36][37][38] Neelakandan and co-workers reported the waveguiding abilities of TCOB complexes derived from salicylideneimine and naphthalideneimine residues. 39,40 Zhang et al prepared several TCOB complexes of 2-hydroxyphenyl imidazole that exhibited excellent electroluminescent properties, high thermal stability and acted as active component for a deep blue emitting OLED material. 41,42 Such benzimidazole based TCOBs with extended π-conjugation and structural rigidity are considered ideal for developing bright, blue-emissive materials, and as promising candidates for the development of sensors and solar cells.…”

Isomer Selective Thermosalience and Luminescence Switching in Organic Crystals

“…We have recently reported that boron complexes of salicylideneimine and naphthalidenimine yielded adaptable single crystals. , In this context, we were interested to investigate if fine-tuning their structure would afford dynamic crystals exhibiting stimuli-responsive properties. Herein, we report the mechanical and luminescence properties of two naphthalidenimine–boron complexes (Figure ) wherein the previously used flexible side chains were rationally substituted with a rigid aromatic unit containing the (diethyl)­amino group.…”