Metalloamphiphiles with [Cu 2 ] and [Cu 4 ] Headgroups: Syntheses, Structures, Langmuir Films, and Effect of Subphase Changes

The metalloamphiphiles [(L PM18 ) 2 Cu 2 Cl 2 ] · H 2 O ( 1 ), [(L PMtax ) 2 Cu 2 Cl 2 ] · 2MeOH ( 2 ), [(L OF18 ) 2 Cu 2 Cl 2 ] ( 3 ), [(L OF18 ) 2 Cu 4 (μ 4 ‐O)(μ 2 ‐OAc) 4 ] ( 4 ), [(L OF14 ) 2 Cu 4 (μ 4 ‐O)(μ 2 ‐OAc) 4 ] ( 5 ) were synthesized and characterized by means of several spectroscopic and spectrometric methods. The acronyms L PMC18 , L PMtax , L OF18 , and L OF14 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 P $\bar {1}$ space groups. The average Cu–O phenolate and Cu–N imine bond lengths are approximately 2.0 Å. Species 1 – 5 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)