Synthesis, spectral properties and crystal structures of copper(II) isonicotinates, first example of uncoordinated isonicotinates

The syntheses and crystal structures of solid complexes [Cu(en)2(H2O)2](isonic)2 and [Cu(isonic)(dien)(H2O)1.5]·0.5SO4·2.5H2O (en=ethylenediamine; dien=diethylenetriamine; isonic=isonicotinate) are reported. The crystal structure of [Cu(en)2(H2O)2](isonic)2 comprises [Cu(en)2(H2O)2]2+ cations and isonicotinate anions. To our knowledge, this is the first example which contains uncoordinated isonicotinate anions. The crystal structure of [Cu(isonic)(dien)(H2O)1.5]·0.5SO4·2.5H2O contains two cations [Cu(isonic)(dien)(H2O)]+ and [Cu(isonic)(dien)(H2O)2]+, sulfate anions and water molecules. The SO42− anion takes part in an extensive system of hydrogen bonds including both uncoordinated and partially also coordinated water molecules. Based on the molecular structure the electronic, IR and ESR spectra are discussed.