β-Cyclodextrin-nickel biomacromolecular host system for sustainable ligand-free aqueous CC and CN cross-couplings of aryl chlorides: Toward donor-π-acceptor distyrylbenzene chromophores.

A sustainable, ligand-free aqueous method for activating aryl chlorides has been established using a β-cyclodextrin-nickel biomacromolecular host catalyst (Ni-MNPCD) with zinc powder as an in-situ reductant. The amphiphilic β-cyclodextrin (β-CD) structure creates a confined hydrophilic-hydrophobic microenvironment that stabilizes low-valent nickel species through weak coordination and surface-capping interactions, while concurrently facilitating substrate orientation and solubilization through host-guest inclusion. In the absence of ligands and under aqueous conditions, the catalyst effectively facilitates both Mizoroki-Heck and Buchwald-Hartwig cross-coupling reactions of aryl chlorides, yielding isolated products of up to 90% with significant turnover performance (TON = 128.6; TOF = 16.1 h-1). Hot-filtration and recyclability studies validate the heterogeneous characteristics of the catalytic process and the structural integrity of the Ni-MNPCD catalyst through numerous cycles. Quantitative measurements of green chemistry, such as E-factor, process mass intensity, and atom economy, further validate the sustainability of the established system. The aqueous catalytic protocol was further applied to the synthesis of donor-π-acceptor distyrylbenzene (DSB) derivatives, which demonstrate solvent- and pH-responsive photophysical properties, highlighting their significance as functional chromophores for forthcoming structure-property studies concerning optoelectronic and sensing materials.