Metallo supramolecular assemblies of bis-squaraines by allosteric Ca2+ ion binding

Org Lett. 2007 May 10;9(10):1999-2002. doi: 10.1021/ol070582q. Epub 2007 Apr 20.

Abstract

Alkyl chain tethered bis-squaraines bind to Ca2+ ions through the participation of the negatively charged oxygen of the central cyclobutene moiety to form folded H-type aggregates. The initially formed Ca2+ complex is preorganized to facilitate cooperative allosteric binding of Ca2+, resulting in the formation of extended supramolecular arrays. The electronic absorption, IR, and ESI-MS studies support the formation of metallo supramolecular architectures of the folded H-type dimers of the bis-squaraines.