Universal `bond valence versus bond length' correlation curve for manganese–oxygen bonds

The oxidation‐state independent `bond valence ( s ) versus bond length ( r )' correlation curve for manganese–oxygen bonds has been closely approximated using the modified two‐parameter Trömel s = f ( r ) function [Trömel (1983). Acta Cryst. B 39 , 664–669], s = [( r 0 − l )/( r − l )] 2 , where r 0 = 1.763 (2) Å and l = 1.148 (9) Å. The r 0 and l refinable parameters of the above function can be regarded as the alternative bond‐valence parameters intended for use in the modern bond‐valence model [Brown (2009). Chem. Rev. 109 , 6858–6919] in cases where the traditional bond‐valence parameters ( r 0 ; n ) and ( r 0 ; b ) fail.