In general, if the atoms that make up the ring contain heteroatoms, such rings become heterocycles, and organic compounds containing heterocycles are called heterocyclic compounds. An article called A novel crystal structure of {tris[4-(1H-pyrazol-3-yl-κN2)-3-azabut-3-enyl]amine-κN}iron(II) bis(tetrafluoridoborate) methanol monosolvate featuring a low-spin configuration, published in 2015-12-01, which mentions a compound: 948552-36-1, Name is 1H-Pyrazole-5-carbaldehyde, Molecular C4H4N2O, Electric Literature of C4H4N2O.
Mononuclear complexes are good model systems for evaluating the effects of different ligand systems on the magnetic properties of iron(II) centers. A novel crystal structure of the title compound, [Fe(C18H24N10)](BF4)2·CH3OH, with one mol. of methanol per formula unit exhibits a strictly sixfold coordination sphere associated with a low-spin configuration at the metal center. The incorporated methanol solvent mol. promotes extended hydrogen-bonding networks between the tetrafluoridoborate anions and the cationic units. A less constrained crystal structure regarding close contacts between the tetrafluoridoborate anions and the cationic units allows a spin transition which is inhibited in the previously published hydrate of the title compound
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