N-(1,10-Phenanthrolin-5-yl)-4-(2-pyridyl)benzamide monohydrate

In the title molecule, C24H16N4O·H2O, the benzene ring of the 1,10-phenanthroline group and that of the 2-phenylpyridine group are respectively twisted by 67.9 (1) and 15.3 (3)° from the carbamoyl group defined by the plane of the O=C—N group of atoms. The water molecule is hydrogen bonded to one of the phenanthroline N atoms. In the crystal structure, significant π–π stacking interactions occur, with centroid-to-centroid separations in the range 3.567–3.681 (2) Å.

In the title molecule, C 24 H 16 N 4 OÁH 2 O, the benzene ring of the 1,10-phenanthroline group and that of the 2-phenylpyridine group are respectively twisted by 67.9 (1) and 15.3 (3) from the carbamoyl group defined by the plane of the O C-N group of atoms. The water molecule is hydrogen bonded to one of the phenanthroline N atoms. In the crystal structure, significantstacking interactions occur, with centroid-tocentroid separations in the range 3.567-3.681 (2) Å . H atoms treated by a mixture of independent and constrained refinement Á max = 0.30 e Å À3 Á min = À0.23 e Å À3 Table 1 Hydrogen-bond geometry (Å , ). edta (a sacrificial electron donor) into molecular hydrogen can be driven by a condensation product of [Ru(bpy) 2 (5-aminophen)] 2+ and PtCl 2 (4,4'-dicarboxy-bpy) (bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline) with a quantum efficiency of ca 0.01. N- (1,10-phenanthrolin-5-yl)-4-carbamoyl-4'-carboxy-2,2'-bipyridine, which is considered a structural analog of the title compound (I), is employed as a bridging spacer connecting the two different metal centers (Ozawa et al., 2006). In order to improve the quantum efficiency in the light-driven H 2 formation, efforts have been made to clarify the mechanism of this photoinduced process and also to develop the more highly efficient photo-hydrogen-evolving molecular devices. The new bridging spacer (I) was prepared to evaluate the change in photocatalytic efficiency upon replacing the bpy attached to the Pt II center with a phenylpyridinate ligand. We have already succeeded in preparing and testing the corresponding Ru II /Pt II complex but, unfortunately, the compound was found to be ineffective towards the edta-based reduction of H 2 O into H 2 , which will be separately reported elsewhere in a future publication.

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The molecular structure of (I) is shown in Fig. 1. The water is hydrogen bonded to one of the nitrogen atoms of the phen moiety ( Table 1). The phen moiety is slightly deformed from an ideal planar geometry, presumably due to the π-π stacking interactions formed in the crystal, as discussed below. The C1-C3 and the C8-C10 groups of atoms are shifted from the central benzene plane of phen, defined with atoms C4-C7, C11 and C12, in such a manner that the C1-C3 and the C8-C10 units are shifted to opposite sides of the benzene plane. The two pyridyl planes within phen, i.e., the planes defined with atoms N1 and C1-C5 and atoms N2 and C6-C10, are declined with respect to the central benzene plane by 3.7 (1) and 2.5 (1)°, respectively. The carbamoyl group defined by the plane of atoms C13, O1, and N3 is twisted with regard to the benzene ring of phen at an angle of 67.9 (1)°. The carbamoyl plane is also declined by 15.3 (3)° with respect to the benzene plane of the phenylpyridine moiety defined with atoms C14-C19. The dihedral angle between the plane defined with atoms C14-C19 and that with atoms N4 and C20-C24 is 5.6 (2)°, which corresponds to the dihedral angle of the two aromatic rings within the phenylpyridine moiety. In the best plane calculations carried out for the above-mentioned five aromatic rings, the 6-atom r.m.s. deviations are in the range of 0.003-0.015 Å, revealing that all these rings have an essentially planar geometry.
As shown in Fig. 2, the phen moiety has a π-stack to the adjacent phen moieties to give a one-dimensional stack in the crystal. As shown in Fig. 3, one is considered as a strong stack with almost full overlap of the phen moieties, while the other as a relatively weak stack based on the partial overlap of the phen moieties. The interplanar separations between the two aromatic systems for the former and the latter geometries are 3.52 (2) and 3.43 (2) Å, respectively. On the other hand, the phenylpyridine moiety forms a π-stack dimer with the interplanar separation 3.48 (11) Å. supplementary materials sup-2 Experimental A suspension of 4-(2-pyridyl)benzoic acid . 0.5H 2 O (0.25 g, 1.2 mmol) in 10 ml of thionyl chloride was refluxed for 3 h.
The resulting solution was evaporated to dryness and the residue was dried in vacuo to give 4-(2-pyridyl)benzoil chloride.
This was dissolved in 20 ml of anhydrous CH 2 Cl 2 . To a solution of 5-amino-1,10-phenanthroline (0.20 g, 1.0 mmol) and triethylamine (0.5 ml) in a 1:1 mixture of anhydrous CH 2 Cl 2 and anhydrous acetonitrile (100 ml) under cooling in an ice bath was added the former solution under Ar over 30 min. After stirring for 3 days at room temperature, the solution was evaporated to dryness. The residue was washed with aqueous 5% NaHCO 3 solution (20 ml), and collected by filtration. Hydrogen atoms of a water molecule were refined isotropically. In the final difference Fourier map, the highest peak was located 0.63 Å from atom H3. The deepest hole was located 0.38 Å from atom H3.

Special details
Experimental. The first 50 frames were rescanned at the end of data collection to evaluate any possible decay phenomenon. Since it was judged to be negligible, no decay correction was applied to the data.