Redetermination of the crystal structure of 5,14-dihydro-6,17-dimethyl-8,15-diphenyldibenzo(b,i)(1,4,8,11)

C 32 H 28 N 4 , monoclinic, P 2 1 / c (no. 14), a = 17.7218(4) Å, b = 20.7769(5) Å, c = 14.9434(3) Å, β = 113 . 598 ( 3 ) ° , V = 5042.1(2) Å 3 , Z = 8, R gt ( F ) = 0.0519, wR ref ( F 2 ) = 0.1544, T = 294 K.

solvent mixture of chloroform and xylene in the ratio of 1:1. X-ray crystallography proved the structure to be a known compound [6,7].

Experimental details
The C-bound H atoms were geometrically placed (C-H = 0.93-0.96 Å) and refined as riding with U iso (H) = 1.2-1.5 U eq (C). The N-bound H atom was located in a difference map and refined with N-H = 0.86 ± 0.01 Å. The hydrogen atoms of three methyl groups, i.e. the C19-, C32-and C64-methyl groups, were modelled over two positions of equal weight and rotated 60°to each other. A number of reflections were omitted from the final cycles of refinement owing to poor agreement; see the CIF for details.

Comment
The crystal structure of the title macrocycle, (I), has been reported previously [6]; the molecule has also been characterised crystallographically as its 1:1 1,2-dichloroethane solvate [7]. In a recent study, the crystal structure [8] of the all methyl derivative of (I) was re-investigated [5]. The new data allowed a definitive analysis of the nature of the bonding in the N=C-C(H) = C-N(H) residue. The improved data reported here for (I) has similarly allowed a resolution of the bonding in the four N=C-C(H)-C-N(H) residues in the two independent molecules of (I).
Two independent molecules comprise the crystallographic asymmetric-unit of (I); their molecular structures are shown in the figure (35 % probability ellipsoids). To a first approximation, the molecular conformations of the independent molecules are equivalent (see below). The four nitrogen atoms define an approximate plane and feature intramolecular secondary Considerable delocalisation of π-electron density is noted in the formally N=C-C(H)=C-N(H) residues. Using the C14-N1(H)-C1-C2-C3=N2-C4 sequence as an example for the three remaining residues, the C3=N2 bond of 1.318(3) Å is consistent with a formal double bond. However, the experimentally equivalent C1-C2 and C2-C3 bond lengths, at 1.395(3) and 1.411(3) Å, respectively, are longer and shorter than formal double and single bonds, respectively. Further, the C1-N1 bond is shorter, at 1.337(3) Å, than that expected for a C-N single bond. The delocalisation extends to the fused six-membered rings as seen in the C4-N2 and C14-N1 bond lengths of 1.412(3) and 1.408(3) Å, respectively. Thus, with the possible exception of the C3=N2 bond, the bonding in the remaining atoms of the C14-N1(H)-C1-C2-C3=N2-C4 sequence more closely resembles the bonding, i.e. with extensive delocalisation of π-electron density over this residue, when doubly-deprotonated (I) complexes to M = copper(II) [9] and M = nickel(II) [10], defining square-planar MN 4 geometries. A search for directional interactions in the crystal of (I), with the aid of PLATON [11], only revealed a weak N-boundphenyl-C-H···π(terminal phenyl) [C16-H16···Cg(C52-C57) i : H16···Cg(C52-C57) i = 2.96 Å, C16···Cg(C52-C57) i = 3.723(3) Å and angle at H16 = 140°for symmetry operation (i): x, 1/2 − y, 1/2 + z] contact. These interactions occur between the independent molecules within a helical arrangement of molecules along the b-axis. This conclusion is supported by an analysis of the calculated Hirshfeld surfaces. Thus, with the program suite CrystalExplorer [12] and following standard procedures [13], the surface contacts were evaluated. Previous work [14] has shown how useful such an approach can be in distinguishing independent molecules in a crystal and how these results can confirm space group assignment.
The analysis of surface contacts in (I) indicates shows that 64.1 % of all surface contacts are due to H···H contacts.