The correlation between metal oxidation state and bond valence parameters for M-O bonds (M = V, Fe and Cu). A simple method to search for the metal oxidation-state independent parameter pairs

Based on the latest available crystal data and the reported bond valence parameters, the linear correlation between the bond valence parameter R-0 with B = 0.37A for M-O bonds (M = V, Fe and Cu) and the metal oxidation state n is shown for the first time. For V-O bonds, a linear equation of R-0 similar to n is perfectly established as R-0 = 0.0250n + 1.674 (n = 2-5). Similarly, a linear equation for Fe-O bonds is fitted as R-0 = 0.0335n + 1.648 (n = 2-4), as well as R-0 = 0.0855n + 1.482 (n = 1-3) for Cu-O bonds fitted properly. In addition, the linear correlation between R-0 and n within certain range of B values for V-O and Fe-O bonds is also established. Consequently, the oxidation-state independent parameters (R-0, B) of (1.788, 0.32 A) for V-O bonds and (1.795, 0.30 A) for Fe-O bonds can be derived from the zero slope of the R-0 similar to n straight lines. However, a similar parameter pair for Cu-O bonds cannot be found using this unique approach.