Premium
Two‐Step versus One‐Step Spin Transitions in Iron(II) 1D Chain Compounds
Author(s) -
Bauer Wolfgang,
Scherer Wolfgang,
Altmannshofer Sandra,
Weber Birgit
Publication year - 2011
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.201001363
Subject(s) - chemistry , spin crossover , spin transition , crystallography , thermal hysteresis , solvent , toluene , propane , medicinal chemistry , stereochemistry , organic chemistry , phase transition , physics , quantum mechanics
Eleven iron(II) 1D coordination polymers with the general formula [FeL eq (L ax )] · solvent were synthesised and characterised, where L eq = (E,E)‐{diethyl 2,2′‐[1,2‐phenylenebis(iminomethylidyne)]bis(3‐oxobutanato) (2‐)‐ N , N′ ,O 3 ,O 3 ′} (L1) and {[3,3′]‐[1,2‐phenylenebis(iminomethylidyne)]bis(2,4‐pentane‐dionato)(2‐)‐ N , N′ ,O 2 ,O 2 ′} (L2); L ax = 4,4′‐bipyridine (bipy), 1,2‐bis(4‐pyridyl)ethane (bpea) and 1,3‐bis(4‐pyridyl)propane (bppa) and solvent = MeOH, EtOH and toluene (Tol). [FeL1(bpea)] · MeOH ( 3· MeOH) shows an abrupt one‐step spin crossover with thermal hysteresis(27 K) and [FeL2(bppa)] · MeOH ( 2· MeOH), [FeL2(bpea)] ( 4 ), [FeL2(bpea)] · 0.25MeOH ( 4· 0.25MeOH) and [FeL1(bipy)] · MeOH ( 5· MeOH) show a two‐step spin transition with an IP at γ HS ≈ 0.5 (IP is intermediate plateau and γ HS is high‐spin mol fraction) and up to 50 K wide hysteresis loops ( 5· MeOH). [FeL1(bppa)] ( 1 ), [FeL2(bppa)] · EtOH ( 2· EtOH) and [FeL1(bpea)] · 1.5Tol ( 3· 1.5Tol) show an abrupt incomplete spin transition that stops at γ HS ≈ 0.5; for [FeL1(bppa)] · 0.25MeOH ( 1· 0.25MeOH) and [FeL1(bpea)] ( 3 ), the spin transition is gradual and incomplete. The X‐ray crystal structures of six complexes were determined ( 1 , 2· MeOH, 3· MeOH, 3· 1.5Tol, 4· 0.25MeOH and 5· MeOH). In the case of 4· 0.25MeOH, the crystal structures for the HS and LS states were dertermined; for compounds 1 , 2· MeOH and 3· 1.5Tol, the crystal structure of the HS and the IP state was investigated. For all complexes, the iron(II) centre is located in a distorted octahedral coordination sphere. Each axially coordinated ligand “connects” two iron(II) centres, which results in the formation of extended 1D chains with varying structures from linear (bipy) over steplike (bpea) to zigzag (bppa). Analysis of the intermolecular interactions reveals that the hysteresis width depends on both the stiffness of the axial ligand and the number of intermolecular contacts, while zigzag chains support stepwise spin transitions.