Intermolecular Interactions in Solid-State Metalloporphyrins and Their Impacts on Crystal and Molecular Structures

A variable-temperature
(VT) crystal structure study of [Fe­(TPP)­Cl] (TPP2– = meso-tetraphenylporphyrinate) and Hirshfeld surface
analyses of its structures and previously reported structures of [M­(TPP)­(NO)]
(M = Fe, Co) reveal that intermolecular interactions are a significant
factor in structure disorder in the three metalloporphyrins and phase
changes in the nitrosyl complexes. These interactions cause, for example,
an 8-fold disorder in the crystal structures of [M­(TPP)­(NO)] at room
temperature that obscures the M–NO binding. Hirshfeld analyses
of the structure of [Co­(TPP)­(NO)] indicate that the phase change from I4/m to P1̅ leads
to an increase in void-volume percentage, permitting additional structural
compression through tilting of the phenyl rings to offset the close-packing
interactions at the interlayer positions in the crystal structures
with temperature decrease. X-ray and neutron structure studies of
[Fe­(TPP)­Cl] at 293, 143, and 20 K reveal a tilting of the phenyl groups
away from being perpendicular to the porphyrin ring as a result of
intermolecular interactions. Structural similarities and differences
among the three complexes are identified and described by Hirshfeld
surface and void-volume calculations.