trans-Bis(4,7-diphenyl-1,10-phenanthroline-κ2 N,N′)bis(nitrato-κ2 O,O′)zinc(II)

The title compound, [Zn(NO3)2(C24H16N2)2], is a twofold axially symmetric coordination compound. Given that the Zn—O interactions [2.4926 (15) and 2.6673 (15) Å] can be considered as weakly bonding and the nitrate ions share the same C 2 axis of the Zn(dpp)2 fragment (dpp is 4,7-diphenyl-1,10-phenanthroline), these anions belong to the coordination sphere of Zn2+, leading to a complex with an overall coordination number of 8 for the metal ion.

The title compound, [Zn(NO 3 ) 2 (C 24 H 16 N 2 ) 2 ], is a twofold axially symmetric coordination compound. Given that the  and 2.6673 (15) Å ] can be considered as weakly bonding and the nitrate ions share the same C 2 axis of the Zn(dpp) 2 fragment (dpp is 4,7-diphenyl-1,10-phenanthroline), these anions belong to the coordination sphere of Zn 2+ , leading to a complex with an overall coordination number of 8 for the metal ion.

Experimental
Crystal data [Zn(NO 3
The title compound comprises a twofold axial symmetric Zn 2+ coordination compound containing two dpp ligands and two nitrato ions (see Scheme). The asymmetric unit comprises half of the complex, in which the metal centre and the O2, N3,  et al., 2006). This feature, in addition to the existence of a common twofold axis with the [Zn(dpp) 2 ] 2+ fragment, is a clear indication that the nitrate is effectively interacting with the metallic centre. The octahedral cis and trans angles are highly deviated from the ideal value. Considering the centre of gravity (C g ) of the O-N-O chelating moieties as the points where angles are measured, the cis angles range from ca 76.1 (N2-Zn1···C g ) to 104.89 (4)° (N2-Zn1-N1 i ; symmetry code (i): -x, y, 0.5 -z). Conversely, the trans angles can be as small as 152.24 (7)° (N2-Zn1-N2 i ). The average planes of the peripheral phenyl moieties of dpp form angles of ca 43.4 and 49.6° with the average plane of the phenanthroline fragment.
The crystal structure is rich in weak supramolecular interactions such as π-π stacking, C-H···π (Babu, 2003) and C-H···O. Due to the complexity of the network created by these intermolecular interactions they have been omitted from Figure 2 (crystal packing) for simplicity. Weak π-π stacking interactions occur between pairs of symmetry-equivalent peripheral phenyl substituents, with distances between the centroids (C t ) of ca 3.80 and 4.18 Å. C-H/π interactions occur between five H atoms and neighbouring aromatic rings, with 〈(C-H···C t ) larger than ca 147° and d H··· C t in the ca 2.80-3.45 Å range. C-H···O hydrogen bonding interactions occur between four H-atoms and neighbouring O-atoms from the nitrato groups: 〈(DHA) larger than ca 140° and internuclear D···A distances in the ca 3.29-3.50 Å range.
supplementary materials sup-2 Experimental Starting chemicals were purchased from commercial sources and were used as received without any further purification.
The title compound was prepared in a Teflon-lined reaction vessel under static hydrothermal conditions in an oven preheated at 160 °C. The total reaction time was of 2 days. The reactive mixture was prepared by using a Zn(NO 3 ) 2 .6H 2 O: dpp (4,7-diphenyl-1,10-phenanthroline) molar ratio of about 2: 1. After reacting, a large amount of brown-red crystals could be directly isolated from the contents of the reaction vessel.