The redox-active fac-[MoV(mp)3]− (mp: o-mercaptophenolato) bearing asymmetric O- and S-cation binding
sites can bind with several kinds of metal ions such as Na+, MnII, FeII, CoII, NiII, and CuI. The fac-
[MoV(mp)3]− metalloligand coordinates to Na+ to form the contact ion pair {Na+(THF)3[fac-MoV(mp)3]}
(1), while a separated ion pair, n-Bu4N[fac-MoV(mp)3] (2), is obtained by exchanging Na+ with n-Bu4N+.
In the presence of asymmetric binding-sites, the metalloligand reacts with MnIICl2·4H2O, FeIICl2·4H2O,
CoIICl2·6H2O, and NiIICl2·6H2O to afford UV-vis-NIR spectra, indicating binding of these guest metal
cations. Especially, for the cases of the MnII and CoII products, trinuclear complexes, {M(H2O)(MeOH)-
[fac-MoV(mp)3]2}·1.5CH2Cl2 (3·1.5CH2Cl2 (M = MnII), 4·1.5CH2Cl2 (M = CoII)), are successfully isolated
and structurally characterized where the M are selectively bound to the hard O-binding sites of the
fac-[MoV(mp)3]−. On the other hand, a coordination polymer, {CuI(CH3CN)[mer-MoV(mp)3]}n (5), is
obtained by the reaction of fac-[MoV(mp)3]− with [CuI(CH3CN)4]ClO4. In sharp contrast to the cases of 1,
3·1.5CH2Cl2, and 4·1.5CH2Cl2, the CuI in 5 are selectively bound to the soft S-binding sites, where each
CuI is shared by two [MoV(mp)3]− with bidentate or monodentate coordination modes. The second notable
feature of 5 is found in the geometric change of the [MoV(mp)3]−, where the original fac-form of 1 is
isomerized to the mer-[MoV(mp)3]− in 5, which was structurally and spectroscopically characterized for the
!rst time. Such isomerization demonstrates the structural "exibility of the [MoV(mp)3]−. Spectroscopic
studies strongly indicate that the association/dissociation between the guest metal ions and metalloligand
can be modulated by solvent polarity. Furthermore, it was also found that such association/dissociation
features are signi!cantly in"uenced by coexisting anions such as ClO4
− or B(C6F5)4
−. This suggests that
coordination bonds between the guest metal ions and metalloligand are not too static, but are suf!ciently
moderate to be responsive to external environments. Moreover, electrochemical data of 1 and 3·1.5CH2Cl2
demonstrated that guest metal ion binding led to enhance electron-accepting properties of the metalloligand.
Our results illustrate the use of a redox-active chalcogenolato complex with a simple mononuclear structure
as a multifunctional metalloligand that is responsive to chemical and electrochemical stimuli.
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