Crystal structure of (pyridin-2-ylmethylidene)(triphenylmethyl)amine

The title Schiff base compound, C25H20N2, crystallizes with two independent molecules (A and B) in the asymmetric unit. In both molecules, the imine group is approximately coplanar with the pyridine ring, with N—C—C—N torsion angles of 170.1 (3) and −172.0 (3) Å. In the crystal, A and B dimers are linked by pairs of C—H⋯π interactions and further C—H⋯π bonds link the dimers into a three-dimensional network.

Cg1 is the centroid of the N1, C1-C5 ring, Cg2 of ring C8-C13, Cg3 of ring C14-C19, Cg4 of ring C20-C25, Cg5 of ring N1 0 , C1 0 -C5 0 , Cg6 of ring C8 0 -C13 0 , Cg7 of ring C14 0 -C19 0 and Cg8 of ring C20 0 -C25 0 . new generation of memory devices, multifunctional materials, and other magnetic applications (Murray, 2008;Goodwin, 2004 and references therein). The 2-pyridylmethanimine Schiff base derivative has been used as a chelating ligand in mononuclear iron(II) SCO complexes as they often possess field strengths that lie within the right region to facilitate temperature-mediated switching between the high spin (HS) and low spin (LS) states of the iron(II) centers (Guionneau et al., 2001;Capes et al., 2000;Létard et al., 1998;Létard et al., 1997). These ligands are also able to form non-covalent interactions such as hydrogen bonding and weaker electrostatic contracts, which will help to provide diversity to the architectures of structures, and can be associated with subtle effects on the molecular magnetic properties of compounds.  (Létard et al., 1997). The crystal structure has been studied at room temperature (HS state) and at 140 K (LS state) suggests that the cooperativity may be attributed to intermolecular π-π stacking between phenyl rings and crucially the strength of the C-H···S interactions. Following the above, a family of iron(II) compounds containing the 2-pyridyl-  et al., 2000). Our interest in the mononuclear iron(II) SCO complexes has led us to prepare a new Nbidentate Schiff base derivative (I), which has the triphenylmethane group attached to the 2-pyridylmethanimine moiety.
It is anticipated that weak non-covalent forces such as C-H···π and π-π interactions will help to stabilize the assembly as well as increase the dimensionality of the structure and may also serve as weak exchange pathways between the magnetic metal center. Herein we report the supramolecular structure of (I), which is mediated by both intra-and intermolecular ef C-H···π interactions.
The N-bidentate Schiff base derivative (I) can be obtained by condensation of 2-pyridinecarboxaldehyde with triphenylmethanamine. Single crystal X-ray diffraction analysis reveals that (I) crystallizes in the chiral orthorhombic space group P2 1 2 1 2 1 , with two molecules (denoted A and B) representing the asymmetric unit as shown in Fig (Table 1). Finally, no classical hydrogen bonding and π-π stacking between adjacent molecules are observed in the crystal structure of (I). Its packing is mainly based on weak ef C-H···π interactions.

S2. Experimental
To a solution of 2-pyridinecarboxaldehyde (1.90 ml, 0.02 mol) in benzene (100 ml), and a few drops of acetic acid as catalyst was added drop wise with triphenylmethanamine (5.20 g, 0.02 mol) at room temperature. The reaction mixture was stirred under reflux at 110 °C. After 6 h of refluxing, the yellow solution was neutralized with Na 2 CO 3 (2 mmol), filtered, and concentrated to dryness in vacuo. The residue was recrystallized from a mixture of CH 2 Cl 2 and petroleum ether (2:1, v:v) to give white crystalline solid of (I

S3. Refinement
The C-bound hydrogen atoms were placed in geometrically idealized positions based on chemical coordinations and constrained to ride on their parent atom positions with a C-H distances of 0.95 Å and with U iso (H) = 1.2U eq (C) for the aromatic H atoms.

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.