Metalloamphiphiles with [Cu2] and [Cu4] Headgroups: Syntheses, Structures, Langmuir Films, and Effect of Subphase Changes



The metalloamphiphiles [(LPM18)2Cu2Cl2]·H2O (1), [(LPMtax)2Cu2Cl2]·2MeOH (2), [(LOF18)2Cu2Cl2] (3), [(LOF18)2Cu44-O)(μ2-OAc)4] (4), [(LOF14)2Cu44-O)(μ2-OAc)4] (5) were synthesized and characterized by means of several spectroscopic and spectrometric methods. The acronyms LPMC18, LPMtax, LOF18, and LOF14 indicate the deprotonated forms of pseudomacrocyclic (PM) and open-frame (OF) ligands based on 2,6-bis(iminomethyl)-4-methylphenol attached to octadecyl (18), trialkoxyamine (tax) and tetradecyl (14) moieties, whereas Cl and OAc indicate chlorido and acetato coligands. Crystal structures were obtained for 4 and 5 that crystallize in triclinic crystal systems with Pequation image space groups. The average Cu–Ophenolate and Cu–Nimine bond lengths are approximately 2.0 Å. Species 15 were analyzed by means of isothermal compression and Brewster angle microscopy (BAM). Moderate collapse pressures of approximately 15 mN m–1 were observed for 3, 4, and 5, while 1 collapses at approximately 30 mN m–1. Species 1, 3, 4, and 5 are responsive to several subphase changes such as temperature and addition of terephthalate ions, which leads to considerable Langmuir film enhancement. In presence of terephthalate the collapse pressure for 3, 4, and 5 nearly doubles, whereas a minimal effect was observed for 1. It appears that as temperature decreases, collapse pressure increases. The variation of pH produced inconclusive data. It is suggested that terephthalate ion interacts with the amphiphiles at a molecular level to generate discrete molecules rather than extended systems.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)