Abstract:
The synthesis of 3-ethynylthienyl- (2.07), 3-ethynylterthienyl- (2.19) substituted qsal
[qsalH = N-(8-quinolyl)salicylaldimine] and 3,3' -diethynyl-2,2' -bithienyl bridging bisqsal (5.06) ligands are described along with the preparation and characterization of eight
cationic iron(III) complexes containing these ligands with a selection of counteranions
[(2.07) with: SCN- (2.08), PF6- (2.09), and CI04- (2.10); (2.19) with PF6
- (2.20); (5.06)
with: cr (5.07), SeN- (5.08), PF6- (5.09), and CI04- (5.10)]. Spin-crossover is observed
in the solid state for (2.08) - (2.10) and (5.07) - (5.10), including a ve ry rare S = 5/2 to
3/2 spin-crossover in complex (2.09). The unusal reduction of complex (2.10) produces a
high-spin iron(I1) complex (2.12).
Six iron(II) complexes that are derived from thienyl analogues of bispicen [bispicen =
bis(2-pyridylmethyl)-diamine] [2,5-thienyl substituents = H- (3.11), Phenyl- (3.12), 2-
thienyl (3.13) or N-phenyl-2-pyridinalimine ligands [2,5-phenyl substituents = diphenyl
(3.23), di(2-thienyl) (3.24), 4-phenyl substituent = 3-thienyl (3.25)] are reported
Complexes (3.11), (3.23) and (3.25) display thermal spin-crossover in the solid state and
(3.12) remains high-spin at all temperatures. Complex (3.13) rearranges to form an
iron(II) complex (3.14) with temperature dependent magnetic properties be s t described as
a one-dimensional ferromagnetic chain, with interchain antiferromagnetic interactions
and/or ZFS dominant at low temperatures. Magnetic succeptibility and Mossbauer data
for complex (3.24) display a temperature dependent mixture of spin isomers. The preparation and characterization of two cobalt(II) complexes containing 3-
ethynylthienyl- (4.04) and 3-ethynylterhienyl- (4.06) substituted bipyridine ligands
[(4.05): [Co(dbsqh(4.04)]; (4.07): [Co(dbsq)2(4.06)]] [dbsq = 3,5-dbsq=3,5-di-tert-butylI ,2-semiquinonate] are reported. Complexes (4.05) and (4.07) exhibit thermal valence
tautomerism in the solid state and in solution.
Self assembly of complex (2.10) into polymeric spheres (6.11) afforded the first spincrossover, polydisperse, micro- to nanoscale material of its kind. . Complexes (2.20),
(3.24) and (4.07) also form polymers through electrochemical synthesis to produce
hybrid metaUopolymer films (6.12), (6.15) and (6.16), respectively. The films have been
characterized by EDX, FT-IR and UV-Vis spectroscopy. Variable-temperature magnetic
susceptibility measurements demonstrate that spin lability is operative in the polymers
and conductivity measurements confirm the electron transport properties. Polymer (6.15)
has a persistent oxidized state that shows a significant decrease in electrical resistance.
