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On the Effect of Coordination and Protonation Preferences in the Amphiphilic Behavior of Metallosurfactants with Asymmetric Headgroups
Author(s) -
Lesh Frank D.,
Hindo Sarmad Sahiel,
Heeg Mary Jane,
Allard Marco M.,
Jain Prateek,
Peng Bo,
Hryhorczuk Lew,
Verani Cláudio N.
Publication year - 2009
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200800761
Subject(s) - chemistry , protonation , crystallography , tetraphenylborate , octahedron , deprotonation , coordination complex , nickel , stereochemistry , medicinal chemistry , crystal structure , ion , organic chemistry , metal
The metallosurfactants [Ni II (L t BuODA )(OAc)] ( 1 ), [Ni II (L t BuODA ) 2 ]( 2 ), [Cu II (HL t BuODA )(L t BuODA )]ClO 4 · CH 3 OH ( 3 ), and [Zn II (HL t BuODA ) 2 ](ClO 4 ) 2 ( 4 ) {where HL t BuODA = 2,4‐di‐ tert ‐butyl‐6‐[(octadecyl(pyridin‐2‐ylmethyl)amino)methyl]phenol}were synthesized and characterized in an attempt to establish how coordination modes and protonation preferences relate to amphiphilic behavior. The archetypical compounds [Ni II (L t BuI )(OAc)] · CH 3 OH ( 5 ), [Ni II (L A ) 2 ] · CH 3 OH · H 2 O ( 6 ), [Ni II (L t BuA ) 2 ] · 2CH 3 OH ( 7 ), [Cu II (HL t BuA )(L t BuA )]ClO 4 ( 8 ), and [Zn II (HL t BuA )(L t BuA )]ClO 4 ( 9 ) were synthesized to model the stoichiometric, coordination, and protonation chemistry in the waxy metallosurfactants 1 – 4 . Detailed data analysis and comparison between 1 – 4 and 5 – 9 involved mass spectrometric and spectroscopic methods along with crystallographic determination of 5 ( P 2 1 / c ), 6 ( P $\bar {1}$ ), 7 ( P 2 1 / c ), 8′ (the analogue of 8 with tetraphenylborate counterions, P 2 1 / c ), and 9 ( P $\bar {1}$ ). DFT calculations were used to identify the frontier orbitals, polarizability, and dipole moments. Species 1 – 4 had their compression isotherms measured and monitored by means of Brewster angle miscroscopy. The nickel‐containing 1 is square planar, while 2 has a neutral octahedral core with two deprotonated ligands. The five‐coordinate copper‐containing 3 has a monocationic core associated with one protonated ligand, whereas the dicationic zinc‐containing 4 has a four‐coordinate core with protonated ligands. It was observed that Langmuir films of 1 display approximately half of the average molecular area observed for 2 – 4 and that the flexibility and coordination number of the cores foster distinctive collapse mechanisms. Therefore, careful choice of the metal ion leads to control of surfactant‐to‐metal ratio, selection of coordination modes and structural properties, and the understanding of the protonation preferences of the ligands. This information will play an important role in the development of metal‐containing responsive films. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)