Spectroscopic and Magnetostructural Correlations in Oxo-Bridged Dinuclear Vanadium(III) Complexes of Potential Biological Significance

Abstract

The synthesis of several dinuclear @-oxo)bis@-carboxylato or diphenylphosphato) divanadium(II1) complexes, [V20(02CR)2Lz] (where L = HB(pz)3-and R = CH3 (I), C6H5 (11), C2H5 (111), and H (IV), or L = HB(3,5-Mezpz)3-and R = CH3 (V)) and [VZ~(~~P(OC~H~)Z)~(HB(~Z)~)~] (X), are described. X-ray crystallographic anal sis of I11 and X gave the following parameters: 111, C~~& Z B~N I~O~V~, P21/n, a = 13.406(3) A, b = 15.313-(3) 1, c = 22.217(4) A, ,8 = 106.75(3)", Z = 4, V = 4367(2) A3; X, C U H~~B~N I~O~P~V~, P21/n, a = 11.944(4) A, b = 20.091(7) A, c = 21.729(16) A, p = 94.38(4)", Z = 4, V = 5199(4) A3. Protonation of the oxo-bridged species with either HC104 or HS03CF3 causes a rapid color change from deep green to pale red and results in the crystallization of the hydroxo-bridged species [VZ(OH)(O~CR)~(HB(PZ)~)~](X) (where R = CH3 and X = C104-(VI) or R = C2H5 (VQ, C6H5 (W), and H (W, and X = CFsS03-) and [ V~( O H ) ( O~P (~~H~>~)~( H B ( P Z )~)~I ( C S 0 3 ) (XI). Crystallographic parameters are as follows: VIIb, C29H39B2F3N1209SV2, P212121. a = 12.309(3) A, b = 16.197(2) A, c = 20.232(2) A, Z = 4, V = 4033.9(9) A3; XI, C56.5H64.5B2F3N120,4,5P2sV2, Pi, a = 12.113-(2) A, b = 14.938(3) A, c = 20.052(4) A, a = 72.88(3)", ,8 = 76.73(3)", y = 87.15(3)", Z = 4, V = 3374.3 (11) A3. In contrast to well-studied oxo-bridged Fe(III) complexes, W-visible, paramagnetic NMR, resonance Raman, and magnetic susceptibility on these V(III) complexes reveal electronic and magnetostructural correlations dependent on the V-0-V angle. Such correlations may be useful in assigning structures to complex biosystems containing the [V@-0)Vl4+ core.in the biochemistry of tunicates. Certain species of tunicates have long been known to concentrate vanadium, primarily as V(III), in their blood cell^.^.^ Upon cell lysis ascidian blood rapidly tums bright red, a characteristic first recognized by H e n~e .~ Although there is no structural data available on the chromophore in "Henze's solution", model compound studies and UV-visible spectroscopic measurements carried out in solution are all consistent with the formation of an oxo-bridged divanadium(III) core.8-10 While X-ray crystallography provides the most definitive and precise structural information on large biomolecules, its application is frequently beset with the difficulties of growing single crystals. In contrast, complementary spectroscopic probes of structure do not suffer as much from this limitation and are readily applicable to aqueous solutions, the ubiquitous biological medium. Hence one of the main goals of our research program is to provide spectro-and magnetostructural relationships for oxo-bridged vanadium dimers. By establishing relationships between the structures of small well-defined molecules, as determined by X-ray crystallography, and spectral and magnetic properties, such as UV-visible and resonance Raman spectroscopies as well as magnetic exchange coupling constants, it may be possible to extract detailed structural data from complex biosystems such as tunicate blood....

Synthesis and Structural Characterization of New Divanada‐ and Diniobaboranes Containing Chalcogen Atoms

“…In many cases, oxametallaboranes have been isolated in low yield. For example, [(h 6 -C 6 Me 6 )RuOB 10 H 13 ] [25] , [(Cp*Mo) 2 B 5 A C H T U N G T R E N N U N G (m 3 -OEt)H 7 ], [36] and nido-[Cp*RhOB 10 H 10 A C H T U N G T R E N N U N G (NEt 3 )] [35] have been isolated in 0.2 %, 5 %, and 8 % yield, respectively. X-ray structure determination: Crystallographic data for compounds 1--4, 6, and 7 are listed in Table 2.…”

Synthesis and Structures of Vanadium(III) and -(IV) Complexes with a Tripodal Quadridentate Ligand Containing Alcoholic and Pyridyl or Imidazolyl Functionality

“…A qualitative molecular orbital N2-V1-N4 148.77(13) N7-V2-N9 148.24 (14) diagram for the V(III)-O-V(III) moiety was proposed by Bond et al [28]. [28,33,34]. Transition moment calculations indicate that the intense transition in the visible region is ascribable to the e g e u *, a metal-localized *-like transition within M-O-M moiety [34,35] DFT calculations for complex 1 also indicate that the intense visible band originates from the e g e u * transition.…”

“…The spectra correspond well with each other, indicating that the solid-state structure was maintained upon dissolution in ethanol. The very intense absorption bands observed in the visible region for the known oxo-bridged dinuclear vanadium(III) complexes (for complex 1, the band at 518 nm with = 2990 mol -1 dm 3 cm -1 ) have been assigned to the ligand-to-metal charge transfer (LMCT) transition of the V(III)-O-V(IIII) moiety based on resonance Raman studies [9,[28][29][30]. This assignment is discussed in greater detail later.…”

“…Based on the resonance Raman studies, this intense band was assigned to a charge transfer transition between the bridging oxo atom and vanadium(III) atom [9,[28][29][30]. A qualitative molecular orbital N2-V1-N4 148.77(13) N7-V2-N9 148.24 (14) diagram for the V(III)-O-V(III) moiety was proposed by Bond et al [28]. [28,33,34].…”

Metal complexes of chalcone analogue: Synthesis, characterization, DNA binding, molecular docking and antimicrobial evaluation

“…[42] Interestingly, a lowenergy intense ligand-to-metal charge transfer transition band is observed at ca 650 nm for this complex, consistent with the trends found in V(III) complexes and assigned for an internal charge transfer transition within the V(III)-O-V(III) moiety. [43][44][45] The electronic spectra of both Pd(II) and Pt(II) complexes show two bands at 304, 305 nm and 373, 425 nm respectively, attributed to 1 A 1g ! 1 A 2g and 1 A 1g !…”