Spin Transition in [Fe(DPEA)(NCS)₂], a Compound with the New Tetradentate Ligand (2-Aminoethyl)bis(2-pyridylmethyl)amine (DPEA):  Crystal Structure, Magnetic Properties, and Mössbauer Spectroscopy

Abstract

The new spin transition compound [Fe(II)(DPEA)(NCS)(2)], where DPEA [(2-aminoethyl)bis(2-pyridylmethyl)amine] is a new tetradentate ligand, has been synthesized, and its structure, magnetic properties, and Mössbauer spectra have been investigated. The crystal structure has been determined by X-ray diffraction at 298 K. The compound crystallizes in the monoclinic system, space group is P2(1)/c, with Z = 4,a = 9.358(1) Å, b = 11.812(2) Å, c = 17.135(2) Å, and beta = 94.5(4) degrees. The distorted [FeN(6)] octahedron is formed from four nitrogen atoms belonging to DPEA and two provided by the cis thiocyanate groups. The two pyridine rings of DPEA are in mer positions. Each molecule is linked to its neighbors by hydrogen-bonding interactions as well as by numerous van der Waals contacts supposed to be responsible for the cooperativity of the system. Variable-temperature magnetic susceptibility measurements (20-290 K) have evidenced a relatively abrupt S = 2 right harpoon over left harpoon S = 0 transition centered at T(1/2) = 138 K. The thermal variation of the high spin state fraction observed by Mössbauer spectroscopy is in agreement with that obtained from magnetic susceptibility measurements. The fitting of Mössbauer and magnetic data with the Ising-like model allowed us to determine the energy gap between the high-spin and low-spin states (Delta(eff) = 835 K) and to estimate the variation of the thermodynamic parameters upon spin transition. The calculated variations of enthalpy (DeltaH = 6.76 kJ mol(-)(1)) and entropy (DeltaS = 49 J mol(-)(1) K(-)(1)) associated with the spin transition are in agreement with those previously observed for iron(II) spin-crossover compounds. The spin conversion is found to be close to a first-order phenomenon.

Synthesis, Structure, Electronic, Redox, and Magnetic Properties of a New Mixed-Valent Mn-Oxo Cluster: [Mn2III,IVO2(N,Nbispicen)2]3+ (N,Nbispicen =N,N-bis(2-pyridylmethyl)-1,2-diaminoethane)

“…[10] Unexpectedly the two primary amino groups of the two N,Nbispicen ligands in the [Mn 2 O 2 (N,Nbispicen) 2 ] 3ϩ cation studied here were found in a "cis" configuration relatively to the Mn 2 O 2 diamond core. This unusual feature gives the potential to assemble two such dimanganese complexes in a dimer of dimers.…”

“…The ligand N,Nbis(2-pyridylmethyl)-1,2-diaminoethane (abbreviation: N,Nbispicen) was prepared by following the procedure in ref [28] . This ligand has also recently been described in ref [10] . Electrochemical Measurements: Cyclic voltammetry was measured using a EGG PAR potentiostat (M 273 model).…”

Spin Crossover in a Family of Iron(II) Complexes with Hexadentate ligands: Ligand Strain as a Factor Determining the Transition Temperature

“…We previously attempted such a study with the iron(II) spin-crossover complexes with the two tetradentate ligands DPEA [(2-amino-A C H T U N G T R E N N U N G ethyl)bis(2-pyridylmethyl)amine] [30] and DPPA [(3-aminopropyl)bis(2-pyridylmethyl)amine] [25] through the enlargement of just one chelate ring from five-to six-membered. The two ligands differ by the presence of an additional methylene unit in the amino aliphatic chain of the DPPA ligand.…”

Photoinduced phenomena and structural analysis associated with the spin-state switching in the[FeII(DPEA)(NCSGlijer1, Hebert2, Trzop3 et al. 2008Phys. Rev. B17250View full textAdd to dashboardCite

“…The [Fe (II) (DPEA)(NCS) 2 ] complex was obtained according to a procedure previously reported 23 . All the crystals used were selected from the same batch.…”