Organic cations controlling the nuclearity of copper(ii) 2,5-pyridinedicarboxylates

Abstract

Depending on the organo-cation mononuclear or polynuclear copper(II) 2,5-pyridinedicarboxylates (L) are formed. Mononuclear complexes with [ML₂(H₂O)] anions are formed when the cations are derived from ethylenediamine (en), N,N,N′,N′-tetramethylethylenediamine (tmen), 1,5-diaminopentane (dap) and 1,4-diazabicyclo[2.2.2]octane (dabco). The use of 4-amino-benzylamine (4aba) as the cation source leads to the hexa-coordinated mononuclear complex [CuL₂(H4aba)₂]·8H₂O. The use of 1,8-diaminooctane (dao) results in a trinuclear complex with the [Cu₃L₆]⁶⁻ anion. The trinuclear anion has copper ions in a square pyramidal and square planar geometry. The use of diethylenetetramine (deta) led to a coordination polymer which had unique hexa and penta coordinated copper ions. It is comprised of dinuclear copper 2,5-pyridinedicarboxylates bridged by mononuclear [ML₂]²⁻ units through side on contacts between the carbonyls on the dinuclear part. The 8-aminoquinolinium cations act as counter ions of the coordination polymer with [CuL₂]²⁻ repeat units. In this coordination polymer, the cations are π-stacked in one dimension. The variation in coordination numbers and the types of chains in the coordination polymers are described.