Dichloridobis{N,N-diethyl-4-[(pyridin-2-yl-κN)diazen­yl]aniline}zinc

Nararak Leesakul; Chaveng Pakawatchai; Saowanit Saithong; Yuthana Tantirungrotechai; Kwanchanok Kwanplod

doi:10.1107/S1600536811022884

. 2011 Jun 18;67(Pt 7):m955–m956. doi: 10.1107/S1600536811022884

Dichloridobis{N,N-diethyl-4-[(pyridin-2-yl-κN)diazenyl]aniline}zinc

Nararak Leesakul ^a,^*, Chaveng Pakawatchai ^a, Saowanit Saithong ^a, Yuthana Tantirungrotechai ^b, Kwanchanok Kwanplod ^a

PMCID: PMC3151768 PMID: 21836935

Abstract

In the title complex, [ZnCl₂(C₁₅H₁₈N₄)₂], the Zn^II cation is coordinated by two N atoms from the pyridine rings of two unidentate N,N-diethyl-4-[(pyridin-2-yl)diazenyl]aniline ligands and two Cl atoms, resulting in a distorted tetrahedral geometry. The ligands are mutually transoid with respect to the metal atom. Weak intermolecular C—H⋯Cl hydrogen bonds and π–π interactions, with centroid–centroid distances of 3.8452 (14) and 3.9932 (14) Å, are found in the crystal packing.

Related literature

For background to azo complexes, see: Arslan (2007 ▶); Santra et al. (2001 ▶); Peacock et al. (2007 ▶); Ohashi et al. (2003 ▶). For applications of azo compounds, see: Millington et al. (2007 ▶); Hallas & Choi (1999 ▶); Ho et al. (1995 ▶); Sharma et al. (2008 ▶). For their photochromic properties, see: Baena et al. (1994 ▶). For structures of related azoimine complexes, see: Leesakul et al. (2010 ▶); Nag et al. (2001 ▶); Pramanik & Das (2010 ▶); Steffen & Palenik (1976 ▶).

Experimental

Crystal data

[ZnCl₂(C₁₅H₁₈N₄)₂]
M _r = 644.96
Monoclinic,
a = 13.4058 (6) Å
b = 13.8797 (6) Å
c = 16.8157 (8) Å
β = 100.562 (1)°
V = 3075.9 (2) Å³
Z = 4
Mo Kα radiation
μ = 1.01 mm⁻¹
T = 100 K
0.17 × 0.17 × 0.06 mm

Data collection

Bruker APEX CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2003 ▶) T _min = 0.780, T _max = 1.000
32570 measured reflections
5410 independent reflections
4547 reflections with I > 2s(I)
R _int = 0.050

Refinement

R[F ² > 2σ(F ²)] = 0.035
wR(F ²) = 0.086
S = 1.06
5410 reflections
374 parameters
H-atom parameters constrained
Δρ_max = 0.50 e Å⁻³
Δρ_min = −0.27 e Å⁻³

Data collection: SMART (Bruker, 1998 ▶); cell refinement: SAINT (Bruker, 2003 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: Mercury (Macrae et al., 2008 ▶); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 ▶) and publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811022884/fj2423sup1.cif

e-67-0m955-sup1.cif^{(27.5KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811022884/fj2423Isup2.hkl

e-67-0m955-Isup2.hkl^{(264.9KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C17—H17⋯Cl1ⁱ	0.95	2.72	3.486 (2)	138

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Symmetry code: (i) Inline graphic .

Acknowledgments

NL acknowledges financial support from the Center for Innovation in Chemistry (PERCH–CIC), the Commission on Higher Education and the Ministry of Education. YT thanks the National Nanotechnology Center (NANOSIM) and the Thailand Research Fund (RSA-5180010) for financial support.

supplementary crystallographic information

Comment

The chemistry of azoimine (—N═N—C═N—) compounds has been known for stabilizing the low-valent metal ions (Arslan, 2007; Santra et al., 2001; Peacock et al.,2007; Ohashi et al., 2003). The imine (—C═N—) and azo (—N═N—) units are ordinary high affinity towards transition metal binding via N hetero atom. Azo compounds are highly colored and commonly utilized in textile industries (Millington et al., 2007; Hallas et al., 1999), optical data storage (Ho et al., 1995) and sensitizer in DSSC (Sharma et al., 2008). In particular, coordination compounds of Zn^II incorporating with azo moiety are extensively used as photoactive materials owing to its interesting photochromic properties (Baena et al., 1994).

Herein, we report the synthesis and crystal structure of a novel Zn^II complex with N,N-diethyl-4-[2-(pyridyl)diazenyl]aniline (C₃₀H₃₆N₈: deazpy), an azoimine ligand. The molecular structure of Zn(C₃₀H₃₆N₈)Cl₂ is a distorted tetrahedral complex (Scheme 1 and Fig.1). The N,N-diethyl-4-[2-(pyridyl)diazenyl]aniline ligand is a bidentate ligand. The chelated coordinations (Nag et al., 2001) between Zn^II and N donor atoms of pyridine and azo moieties are generally observed in the crystal structure. However, in the present work, the Zn^II coordinates to two unidentate deazpy ligands via N(py) atoms [Zn(1)—N(1) = 2.0513 (19) Å, Zn(1)—N(5) = 2.0439 (19) Å] and two Cl atoms [Zn(1)—Cl(1) = 2.2565 (6) Å, Zn(1)—Cl(2) = 2.2713 (6) Å]. These Zn—N bond distances are slightly longer than that of related Zn^II with two unidentate imidazole ligands (Pramanik et al., 2010) giving the Zn—N distances = 2.003 (3) and 2.013 (3) Å. The reported Zn—Cl bond distances in dichlorobis(2-azopyridine)zinc(II) (Nag et al., 2001) complex are averaged to 2.2293 Å while the averaged Zn—Cl bond length in complex of dichlorobis(pyridine)zinc(II) reports at 2.222 Å (Steffen et al., 1976) which are slightly shorter than our complex (average 2.2639 Å). All N—Zn—N, N—Zn—Cl and Cl—Zn—Cl bond angles deviate from 109.5¯, especially for N(5)—Zn(1)—N(1) = 123.54 (8)^o arising from the steric constraints from the deazpy structure. The torsion angles of pyridine-azo-phenyl atoms, C(5)—N(2)—N(3)—C(6) and C(20)—N(6)—N(7)—C(21), are -179.03 (19) and -178.30 (19) ^o, respectively. The dihedral angle of mean planes of pyridine-azo-phenyl rings among two ligands is 57.40(0.04)^o. Within the ligand molecules, the N(py) atoms exist in trans-orientation with respect to the N(azo) atom attached to the phenyl ring. It is as same as that observed from the similar free ligand, N,N-dimethyl-4-[2(pyridyl)diazenyl] aniline (dmazpy) (Leesakul et al., 2010). The N═N distances of the Zn^II complex are 1.286 (3) Å for N2═N3 and 1.280 (3) Å for N6═N7 which are longer than that of the free dmazpy ligand, 1.2566 (16) Å. It is because of the back donation of electron from d¹⁰-Zn^II to π* orbital of the ligands. The strength of the azo bond decreases in comparison with the related free ligand.

The intramolecular C—H···π interactions are found between the phenyl ring of ligand 1 and the pyridine ring (Cg2) of ligand 2 [C(11)—H(11)···π_Cg₂ = 3.303 Å] and vice versa [C(26)—H(26)···π_Cg₁ = 3.550 Å](Fig. 2). In crystal packing, each molecule interacts the adjacent molecules via weak hydrogen-bonding interactions of C(17)—H(17)···Cl(1)ⁱ, [C···Cl = 3.486 (2) Å, symmetry code i: x, -y + 5/2, z - 1/2] (Fig. 2 and Tab. 1). In addition, the intermolecular π–π interactions are found between the phenyl ring of ligands and the adjacent molecules [Cg3···Cg3ⁱⁱ = 3.8452 (14) Å and Cg4···Cg4ⁱⁱⁱ = 3.9932 (14) Å, symmetry code (ii): 2-x, 1-y, 1-z, (iii): 1-x, 1-y, -z] (Fig. 3 and Tab. 2).

Experimental

An acetonitrile solution (20 ml) of the N,N-diethyl-4-[2-(pyridyl)diazenyl]aniline ligand (0.15 g, 0.6 mmol) and ZnCl₂ (0.04 g, 0.3 mmol) was refluxed for 4 h. The filtrate was left at room temperature for 2 weeks. The dark red solids were precipitated and washed it with CH₂Cl₂ and diethylether, respectively for twice times in order to remove the excess ligands. The dark red solids were recrystallized in acetonitrile and methanol (1:2) at 277 K for 10 days. The red crystals were obtained (yield 67%, 0.13 g).