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Iron/2,6‐Di(pyrazol‐1‐yl)pyridine Complexes with a Discotic Pattern of Alkyl or Alkynyl Substituents
Author(s) -
Galadzhun Iurii,
Kulmaczewski Rafal,
Cespedes Oscar,
Halcrow Malcolm A.
Publication year - 2021
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.202100435
Subject(s) - chemistry , pyridine , homoleptic , alkyl , spin crossover , stereochemistry , medicinal chemistry , solvent , mesophase , crystallography , organic chemistry , metal , phase (matter)
Abstract 2,6‐Di(4‐iodopyrazol‐1‐yl)pyridine is converted to 2,6‐di(4‐{alkyn‐1‐yl}pyrazol‐1‐yl)pyridine ( L 1 R; R’=C n H 2 n −3 , n =12, 14, 16) derivatives by Sonogashira reactions. Hydrogenation of these intermediates yields the corresponding 2,6‐di(4‐alkylpyrazol‐1‐yl)pyridine ( L 2 R; R=C n H 2 n +1 ) derivatives. Homoleptic Fe[BF 4 ] 2 complexes of all these ligands were prepared, bearing four long chain substituents in a discotic‐type array. Crystallographic data from two L 1 R ligands imply the alkynyl substituents do not undergo intermolecular interdigitation in the solid state, which could explain the lower crystallinity and ill‐defined spin‐crossover in their iron complexes. Solid [Fe( L 2 R) 2 ][BF 4 ] 2 ( n =12 and 14) exhibit an irreversible, abrupt low→high‐spin event near 350 K, which is not associated with solvent loss and may involve disordering of their alkyl chain conformations. No mesophase behavior was observed from any of these compounds.