TY - JOUR
T1 - Towards Langmuir-Blodgett films of magnetically interesting materials
T2 - Solution equilibria in amphiphilic iron(II) complexes of a triazole-containing ligand
AU - White, Nicholas G.
AU - Feltham, Humphrey L.C.
AU - Gandolfi, Claudio
AU - Albrecht, Martin
AU - Brooker, Sally
PY - 2010
Y1 - 2010
N2 - As a first step towards amphiphilic spin crossover (SCO) systems where the hydrophobic part of the system is introduced by a non-coordinating anion (i.e. where no modification of the ligands to introduce hydrophobic substituents is required), [FeII(OH2)2(C16SO 3)2] and [CoII(OH2) 2(C16SO3)2] have been prepared and reacted with the triazole-containing ligands adpt and pldpt (C 16SO3 = hexadecanesulfonate anion, adpt = 4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole, pldpt = 4-pyrrolyl-3,5-bis(2-pyridyl) -1,2,4-triazole). In the solid state, two HS complexes of the form [Fe II(Rdpt)2(C16SO3)2] and two of the form [CoII(Rdpt)2(CH3OH) 2](C16SO3)2 are obtained, even when a six-fold excess of ligand is used (Rdpt = adpt or pldpt). In solution, the cobalt complexes remain in this form as evidenced by colour, Visible/NIR and IR spectroscopy. For the iron complexes, there is an equilibrium in solution between the neutral high-spin form of the complex [FeII(Rdpt) 2(C16SO3)2] and the dicationic low-spin tris form [FeII(Rdpt)3](C16SO 3)2. Polar solvents favour the dicationic form, while less polar solvents favour the neutral form (as evidenced by solution colour and solution IR spectroscopy). Visible/NIR spectroscopy and Evans' method NMR spectroscopy show the equilibrium can be shifted towards the [Fe II(Rdpt)3](C16SO3)2 form by adding additional ligand to the solution. The X-ray crystal structures of [FeII(adpt)2(C16SO3)2] and [CoII(adpt)2(CH3OH)2](C 16SO3)2·1.33CH3OH are presented. [FeII(adpt)2(C16SO3) 2] has a 2D bilayer structure with alternating layers of polar Fe(adpt)2 centres, and hydrophobic alkyl chains. The complex cations in [CoII(adpt)2(CH3OH)2](C 16SO3)2·1.33CH3OH form 1-D columns in the solid state. The capacity of the amphiphilic complexes [Fe II(pldpt)2(C16SO3)2] and [FeII(adpt)2(C16SO3)2] to self-assemble has been probed at the air-water interface using Langmuir techniques. The pertinent pressure-area isotherms reveal only a low tendency of the complexes to form films.
AB - As a first step towards amphiphilic spin crossover (SCO) systems where the hydrophobic part of the system is introduced by a non-coordinating anion (i.e. where no modification of the ligands to introduce hydrophobic substituents is required), [FeII(OH2)2(C16SO 3)2] and [CoII(OH2) 2(C16SO3)2] have been prepared and reacted with the triazole-containing ligands adpt and pldpt (C 16SO3 = hexadecanesulfonate anion, adpt = 4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole, pldpt = 4-pyrrolyl-3,5-bis(2-pyridyl) -1,2,4-triazole). In the solid state, two HS complexes of the form [Fe II(Rdpt)2(C16SO3)2] and two of the form [CoII(Rdpt)2(CH3OH) 2](C16SO3)2 are obtained, even when a six-fold excess of ligand is used (Rdpt = adpt or pldpt). In solution, the cobalt complexes remain in this form as evidenced by colour, Visible/NIR and IR spectroscopy. For the iron complexes, there is an equilibrium in solution between the neutral high-spin form of the complex [FeII(Rdpt) 2(C16SO3)2] and the dicationic low-spin tris form [FeII(Rdpt)3](C16SO 3)2. Polar solvents favour the dicationic form, while less polar solvents favour the neutral form (as evidenced by solution colour and solution IR spectroscopy). Visible/NIR spectroscopy and Evans' method NMR spectroscopy show the equilibrium can be shifted towards the [Fe II(Rdpt)3](C16SO3)2 form by adding additional ligand to the solution. The X-ray crystal structures of [FeII(adpt)2(C16SO3)2] and [CoII(adpt)2(CH3OH)2](C 16SO3)2·1.33CH3OH are presented. [FeII(adpt)2(C16SO3) 2] has a 2D bilayer structure with alternating layers of polar Fe(adpt)2 centres, and hydrophobic alkyl chains. The complex cations in [CoII(adpt)2(CH3OH)2](C 16SO3)2·1.33CH3OH form 1-D columns in the solid state. The capacity of the amphiphilic complexes [Fe II(pldpt)2(C16SO3)2] and [FeII(adpt)2(C16SO3)2] to self-assemble has been probed at the air-water interface using Langmuir techniques. The pertinent pressure-area isotherms reveal only a low tendency of the complexes to form films.
UR - http://www.scopus.com/inward/record.url?scp=77950216878&partnerID=8YFLogxK
U2 - 10.1039/b923923e
DO - 10.1039/b923923e
M3 - Article
SN - 1477-9226
VL - 39
SP - 3751
EP - 3758
JO - Dalton Transactions
JF - Dalton Transactions
IS - 15
ER -