Bis[1,3-bis(1-benzyl-1H-benzimidazol-2-yl)-2-oxapropane]nickel(II) dipicrate–dimethylformamide–ethanol (1/2/0.25)

In the title compound, [Ni(C30H26N4O)2](C6H2N3O7)2·2C3H7NO·0.25CH3CH2OH, the NiII ion is coordinated in a distorted octahedral environment by four N atoms and two O atoms from two tridendate 1,3-bis(1-benzyl-1H-benzimidazol-2-yl)-2-oxapropane ligands. The crystal structure is stabilized by weak intermolecular C—H⋯O hydrogen bonds and weak π–π stacking interactions [centroid–centroid distance 3.501 (3) Å]. As well as the cation, two anions and two dimethylformamide solvent molecules, the asymmetric unit also contains an ethanol solvent molecule with 0.25 occupancy.


Experimental
Crystal data [Ni(C 30

Data collection
Rigaku R-AXIS SPIDER diffractometer Absorption correction: multi-scan (ABSCOR; Higashi, 1995) T min = 0.948, T max = 0.964 57512 measured reflections 13620 independent reflections 7422 reflections with I > 2(I) R int = 0.100 Refinement R[F 2 > 2(F 2 )] = 0.093 wR(F 2 ) = 0.290 S = 1.14 13620 reflections 1031 parameters 33 restraints H-atom parameters constrained Á max = 1.47 e Å À3 Á min = À0.70 e Å À3 Table 1 Hydrogen-bond geometry (Å , ). There is widespread interest in bis(2-benzimidazolyl)alkanes and their derivatives because of their wide-ranging antivirus activity (Roderick et al., 1972), their importance in selective ion-exchange resins (van Berkel et al., 1995), and the possibility of forming supramolecular aggregates with d 10 metal ions in which discrete macrocycles, 1, 2 and 3-D architectures have been generated (Piquet et al. 1995). We have been interested in utilizing benzimidazolyl substituted tripodal ligands with nitrogen cores to construct supramolecules, which could provide hydrogen bond donor NH groups and π-π stacking interactions (Hendriks et al., 1982). In our work, efforts are focused on the tridentate ligand, 1,3-bis(1benzylbenzimidazol-2-yl)-2-oxopropane, which is similar to the histidine imidazole ligand in its coordination aspects (Wu et al. 2005). Since the two arms of this type of ligand can each rotate freely about an O(apical)-C bond, multicomponent complexes or coordination polymeric networks may be expected to form from the assembly of this ligand with metal ions of low coordination number. Herein, the crystal structure of the title compound is presented. The molecular structure of the cation is shown in Fig. 1. The Ni II ion is coordinated in a disotorted octahedral environment inolving four N atoms and two O atoms from two tridendate ligands with the axial sites occupied by two oxygen atoms.
The crystal structure is stabilized by weak intermolecular C-H···O hydrogen bonds as well as weak π-π stacking interactions with a centroid to centroid distance of 3.501 (3) Å between two benzimidazole ring systems related by the symmetry operator (1-x,-1/2+y,1/2-z).

S3. Refinement
All H atoms were found in difference electron maps and were subsequently refined in a riding-model approximation with C-H distances ranging from 0.95 to 0.99 Å and U iso (H) = 1.2 U eq or U iso (H) = 1.5 U eq for methyl C atoms. The abundance of solvent which is loosely held in the crystal lattice is probably the reason for the lower than normal precision of this structure.

Figure 1
The molecular structure of the cation. Hydrogen atoms have been omitted for clarity and the displacement ellipsoids are shown at the 30% probability level.  Part of the crystal structure with weak hydrogen bonds shown as dashed lines. For clarity the solvent molecules are not included.

Bis[1,3-bis(1-benzyl-1H-benzimidazol-2-yl)-2-oxapropane]nickel(II) dipicrate-dimethylformamide-ethanol
( where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 1.47 e Å −3 Δρ min = −0.70 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0065 (7) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 R-factors(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.