Metal coordination to amphiphilic Ru complexes at the air–water interface

Abstract

We have examined the applicability of ‘metal complex as a ligand’ strategy at the interface by using the Ru complexes acting as a ligand. New amphiphilic ruthenium complexes containing 2,6-bis(1-octadecylbenzimidazolyl)-pyridine (L18), [Ru(L18)(X)] 2+ were synthesized, where X=2,3,5,6-tetrakis(2′pyridyl)pyrazine (tppz) and 1,4-bis(2,2′ : 6′, 2″-terpyridine-4′-yl)benzene (bteb), in which the bis-tridentate ligand (tppz or bteb) of [Ru(L18)(X)] 2+ can act not only as a hydrophilic head group but also as a coordination site to a metal ion from the subphase at the air–water interface. These amphiphilic Ru complexes lead to a stable Langmuir–Blodgett (LB) film formation. The incorporation of metal ion from subphase at the air–water interface was proved by the measurements of π–A isotherms, UV spectra and angular dependent XPS spectra.