The origin of the electronic transitions of mixed valence polyoxovanadoborates [V₁₂B₁₈O₆₀]: from an experimental to a theoretical understanding

Abstract

New insights in the electronic properties of mixed-valence polyoxovanadoborate clusters.

Isolated Mixed-Valence Iron Vanadium Malate and Its Metal Hydrates (M = Fe2+, Cu2+, Zn2+) with Reversible and Irreversible Adsorptions for Oxygen

“…The strong band features below 350 nm can be attributed to the ligand to metal charge transfer (LMCT) of O → M. The broad bands in the region of 500–800 nm correspond to a combination of d → d transitions of the metal ions and intervalence transitions of conjugated vanadium systems . The spectra of 1 – 4 are consistent with the spectra of mixed-valence oxovanadium complexes, whose maximum absorptions are in the region of 500–800 nm varying with V­(V)/V­(IV) ratios. , In addition, the deep colors that are intimately connected with the interatomic oxidation–reduction tendencies are also observed in 1 – 4 , implying a mixture of V­(IV) and V­(V) centers. In Figure S17, the electronic spectrum of 2 -Fe-O 2 shows a weakened and broadened band below 350 nm after adsorption, which corresponds to a change in the ligand to metal charge transfer of O → M.…”

Non-covalent interactions in hexanuclear polyoxidometalates [VIV6B20O50H8]8−. An experimental and theoretical approach

“…The vanadyl stretching band ( V-Ot ) appears at c.a. 920 cm -1 for all studied compounds and in the expected range [9,10,14,[16][17][18][19]21,22,26,[27][28][29][30][31][32]37,[71][72][73]. However, compounds 2 and 3 show a broad band with a shoulder, while compound 1 shows a narrower band than the former ones (Figure 3).…”

“…Recent studies of vanadoborates related to the conductivity of these materials show the importance of the nature of the crystalline packing and all interactions present in it [5][6][7]. The reported VBO structures are mainly composed by six, ten and twelve vanadium centres [2,6], namely the {V 6 -type} clusters: {V 6 B 20 O 50 H n } (n=0, 6,8,12) [8][9][10][11] and {V 6 B 22 O 54 H 10 } [12]; the {V 10 -type} clusters: {V 10 B 28 O 74 H n } [13] and {V 10 B 28 O 74 H n } (n=4, 8) [14,15]; the {V 12 i -type} clusters: {V 12 [11,20,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36], and the {V 12 iii -type} clusters: {V 12 B 32 O 84 H 8 } [38,39]. The most interesting feature of the boron rich structures {V 6 -type}, {V 10 -type} and {V 12 iii -type} is their central oxo-vanadium ring formed by penta-coordinated vanadium units [VO 5 ].…”

Comparisons of bond valences and distances for CO- and N2-bound clusters of FeMo-cofactors

“…1, the X-ray crystal structure has revealed that CO serves as a Z 1 ,m 2 -bridging ligand coordinated to Fe2 and Fe6 by replacing a sulfur atom (S2B) (PDB entry: 4KTV), 15,16 and the second CO terminally binds to Fe6 (PDB entry: 7JRF). 16 Recently, N 2 or N 2 -derived species (PDB entry: 6UG0) The bond valence method originated from Pauling's rule in 1929 21 and developed historically, and is commonly applied in inorganic chemistry [22][23][24][25] and metalloenzyme fields. [26][27][28] It is a classic and valid approach to assess the charge between metal atoms and its bound coordinated atoms, which has been proved as an effective method to evaluate the electron density in a delocalized system.…”

“…The bond valence method originated from Pauling's rule in 1929 21 and developed historically, and is commonly applied in inorganic chemistry 22–25 and metalloenzyme fields. 26–28 It is a classic and valid approach to assess the charge between metal atoms and its bound coordinated atoms, which has been proved as an effective method to evaluate the electron density in a delocalized system.…”