Bond length of perchlorate at different temperatures: X‐ray and neutron comparison

The averages (average deviations from the mean are given in square brackets) of uncorrected Cl—O bond distances in a perchlorate anion from an X‐ray diffraction analysis of (N‐{2‐bis(pyridin‐2‐ylmethyl)amino]ethyl}pyridine‐2‐carboxamidato)(nitric oxide)manganese perchlorate acetonitrile disolvate, Mn(C₂₀H₂₀N₅O)(NO)]ClO₄·2CH₃CN or Mn(PaPy₃)(NO)]ClO₄·2CH₃CN, decrease from 1.447 4] Å at 10 K to 1.428 4] Å at 170 K. The 10 K value is close to the neutron value (1.441 1] Å) at 18 K. Comparisons are made with a second X‐ray study at 30 K 1.444 (8) Å] and to libration‐corrected, density functional theory (DFT), and Cambridge Structural Database (CSD) values.