Diiodido[4′-(4-pyridyl)-2,2′:6′,2′′-terpyridine-κ3 N,N′,N′′]copper(II)

The CuII atom in the title compound, [CuI2(C20H14N4)], has a distorted square-pyramidal coordination formed by the N atoms of the tridentate 4′-(4-pyridyl)-2,2′:6′2′′-terpyridine (pyterpy) ligand and two I atoms; one of the I atoms is in the apical position. In contrast to other known square-pyramidal diiodido- and dibromidocopper complexes of the pyterpy ligand in which metal–halogen distances are significantly different, in the title compound the apical and equatorial Cu—I bonds are almost identical [2.6141 (8) and 2.6025 (8) Å, respectively].

The Cu II atom in the title compound, [CuI 2 (C 20 H 14 N 4 )], has a distorted square-pyramidal coordination formed by the N atoms of the tridentate 4 0 -(4-pyridyl)-2,2 0 :6 0 2 00 -terpyridine (pyterpy) ligand and two I atoms; one of the I atoms is in the apical position. In contrast to other known squarepyramidal diiodido-and dibromidocopper complexes of the pyterpy ligand in which metal-halogen distances are significantly different, in the title compound the apical and equatorial Cu-I bonds are almost identical [2.6141 (8) and 2.6025 (8) Å , respectively].

Comment
Terpyridine and its derivatives have been recently receiving increasing attention not only because of their versatility as building blocks in supramolecular assemblies, but also due to the interesting electronic, photonic and magnetic properties of their transition metal complexes.
This pattern in the Cu-N bonds, is quite typical for the terpy complexes (see Hou et al., 2004;Feng et al., 2006;Kutoglu et al., 1991).
supplementary materials sup-2 Refinement H atoms were positioned geometrically and refined using a riding model with C-H = 0.93 Å(aromatic) and U ĩso (H) = 1.2U eq (C) Figures   Fig. 1. The asymmetric unit of the title compound showing 30% probability ellipsoids.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.