Photocatalytic systems. LVIII. Electron transfer in copper(I)/octacyanomolybdate(V) ion pairs generated by IT excitation

Hennig, H.; Rehorek, Astrid; Rehorek, Detlef; Thomas, Philipp; Bäzold, Dietmar

doi:10.1016/s0020-1693(00)82552-9

Cited by 17 publications

(9 citation statements)

References 8 publications

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“…The CN stretching frequency for 1 was observed at 2162 cm -1 in the IR spectra. The UV−vis spectrum showed the intervalence-transfer (IT) band between Mo IV −CN−Cu II and Mo V −CN−Cu I around 480 nm, which almost corresponded to the optical absorption spectra in the solution of Cu II /[Mo IV (CN) 8 ]. 16a,b …”

Section: Resultsmentioning

confidence: 78%

“…Photoinduced electron transfer is often observed in class II compounds. Hennig et al reported that [Mo IV (CN) 8 ] 4- and Cu 2+ ions form a mixed-valence compound in aqueous solution, which exhibits an IT band around 500 nm. , The excitation of this band causes electron transfer to proceed from Mo IV to Cu II ions and produces a valence isomer, Cu I /[Mo V (CN) 8 ] 3- . 16c, When such a photoinduced electron transfer occurs in the corresponding solid compound, irradiation will change the magnetic properties; i.e., there is the possibility that the unpaired electrons of the produced Mo V ( S = 1 / 2 ) and Cu II ( S = 1 / 2 ) ions interact, leading to the ordering of the spins. Along this scenario, we investigated the photoinduced magnetic effect on a Cu II 2 [Mo IV (CN) 8 ]·8H 2 O ( 1 ) solid and showed the preliminary results of this approach .…”

Section: Introductionmentioning

confidence: 99%

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Photoinduced Magnetization in Copper Octacyanomolybdate

et al. 2005

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This article describes the studies of a photomagnetic cyanide-bridged Cu-Mo bimetallic assembly, Cu(II)(2)[Mo(IV)(CN)(8)].8H(2)O (Cu(II), S = (1)/(2); Mo(IV), S = 0) (1), which has an intervalence transfer (IT) band from Mo(IV)-CN-Cu(II) to Mo(V)-CN-Cu(I) around 480 nm. Wide-angle X-ray scattering and X-ray spectroscopic studies provide precise information about the 3D connectivity and the local environment of the transition metal ions. Irradiating with blue light causes solid 1 to exhibit a spontaneous magnetization (Curie temperature = 25 K). The thermal reversibility is carefully studied and shows the long-time stability of the photoinduced state up to 100 K. Photoreversibility is also observed; i.e., the magnetization is induced by irradiation with light below 520 nm, while the magnetization is reduced by irradiation with light above 520 nm. The UV-vis absorption spectrum after irradiation shows a decrease of the IT band and the appearance of the reverse-IT band in the region of 600-900 nm (lambda(max) = 710 nm). This UV-vis absorption spectrum is recovered to the original spectrum by irradiation with 658-, 785-, and 840-nm light. In this photomagnetic effect, the excitation of the IT band causes an electron transfer from Mo(IV) to Cu(II), producing a ferromagnetic mixed-valence isomer of Cu(I)Cu(II)[Mo(V)(CN)(8)].8H(2)O (Cu(I), S = 0; Cu(II), S = (1)/(2); Mo(V), S = (1)/(2)) (1'). 1' returns to 1 by irradiation of the reverse-IT band, which obeys the scheme for the potential energy surface in mixed-valence class II compounds.

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Section: Resultsmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Photoinduced Magnetization in Copper Octacyanomolybdate

et al. 2005

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“…In Prussian blue analogues, photoinduced magnetization was first observed in hexacyanometalate-based compounds, such as cobalt hexacyanoferrate, in which the electron transfer proceeds from Fe II to Co III by irradiation with visible light. ,,,, A new family of photomagnetic cyanide compounds is born by using light-sensitive building blocks such as octacyanomolybdate or octacyanotungstate. Indeed, the photooxidation of [Mo IV (CN) 8 ] 4− in [Mo V (CN) 8 ] 3− was evidenced in the 1970s by Shirom and co-workers. , Later Hennig and co-workers demonstrated photoinduced electron transfer when the [Mo IV (CN) 8 ] 4− is associated with the Cu II ion to form a donor/acceptor pair in aqueous solution . The excitation of the tridimensional compounds in the intervalence band wavelength (480 nm) induces an electron transfer from Mo IV to Cu II ions and produces the valence isomer Cu I /[Mo V (CN) 8 )] 3− .…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Magnetization on Mo Ion in Copper Octacyanomolybdate: An X-ray Magnetic Circular Dichroism Investigation

et al. 2009

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Recently synthesized copper octacyanomolybdate molecules present interesting photomagnetic properties. Before irradiation, the molecules behave as noncoupled CuII paramagnetic ions (with central diamagnetic MoIV ion), whereas after irradiation (406 nm) they behave as superparamagnetic molecules with CuII ions coupled to the molybdenum ion. The proposed mechanism to explain these photomagnetic properties is based on the photoinduced charge transfer from MoIV (S = 0) to CuII (S = 1/2) leading to the formation of MoV (S = 1/2) and CuI (S = 0) with strong ferromagnetic coupling between MoV and the other CuII spin carriers. This paper presents X-ray magnetic circular dichroism (XMCD) measurements at the molybdenum L2,3 edges. Two bimetallic molecules have been investigated: [Mo(CN)2(CN-CuL)6]8+, L being tris(2-amino)ethylamine and [Mo(CN)6(CN-CuL′2)2], with L′ being N,N′,dimethyl ethylene diamine (labeled MoCu2-Meen). In both cases, before irradiation the XMCD signal is null as expected for diamagnetic MoIV (S = 0). After irradiation, an XMCD signal appears, which directly demonstrates the formation of spin density on the Mo ion. After reaching room temperature, the photoinduced spectral features disappear, indicating the reversibility of the photoinduced process. In the case of MoCu2-Meen, the XMCD experiments allow the observation of an X-ray-induced metastable state made of high-spin MoIV ion (S = 1). The application of the sum rule for isotropic spectra shows that there is no variation of the molybdenum oxidation state during the X-ray-induced magnetic process. From the Mo L2,3 XMCD signal of the X-ray-photoexcited MoCu2-Meen, we obtain an orbital magnetic moment equal to 0.13 μB and a spin magnetic moment equal to 1.22 μB at T = 10 K and H = 6 T. These results demonstrate that the Mo ion in the X-ray-photoinduced excited state of the MoCu2-Meen complex is high-spin MoIV (S = 1).

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“…b Average deviation | h ν calcd − h ν exptl | for ion associates with this ion. c Charge transfer to solvent (water) transition energy. − d Standard redox potential. − e Reorganization energies calculated from eq 13. These should be treated with caution since the electrochemical data are collected over a wide variety of conditions and will not always be entirely appropriate for the conditions under which the OSCT transition is recorded; also see text.…”

Section: Introductionmentioning

confidence: 99%

Vertical Ionization Energies and Electron Affinities of Ions in Solution from Outer-Sphere Charge Transfer Transition Energies

1998

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Outer-sphere charge transfer (OSCT) transitions are shown to correlate with previously published photoelectron emission threshold energies. From these data it is possible to generate a set of parameters, I(D) and I(A), which define these OSCT energies, where I(D) is identified as the solution phase vertical ionization potential, and I(A) is the solution phase vertical electron affinity. An easy procedure for deriving these data for a wide variety of cations and anions is presented. The application of these data leads to a powerful procedure for extracting reorganization and solvation energies of value in a variety of applications.

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Photocatalytic systems. LVIII. Electron transfer in copper(I)/octacyanomolybdate(V) ion pairs generated by IT excitation

Cited by 17 publications

References 8 publications

Photoinduced Magnetization in Copper Octacyanomolybdate

Photoinduced Magnetization in Copper Octacyanomolybdate

Photoinduced Magnetization on Mo Ion in Copper Octacyanomolybdate: An X-ray Magnetic Circular Dichroism Investigation

Vertical Ionization Energies and Electron Affinities of Ions in Solution from Outer-Sphere Charge Transfer Transition Energies

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