Crystal structure of di­chlorido­bis­[2-(phenyl­diazen­yl)pyridine-κN¹]zinc

The structure of the title complex, [ZnCl₂(C₁₁H₉N₃)₂], comprises two 2-(phenyl­diazen­yl)pyridine ligands coordin­ating to a central Zn^II dichloride unit via the pyridyl N-atom donors, resulting in a slightly distorted tetra­hedral geometry. The complex exhibits twofold rotation symmetry, with the rotation axis bis­ecting the zinc cation. The structure is stabilized by weak inter­molecular C—H...Cl inter­actions [C...Cl = 3.411 (2) and 3.675 (2) Å], connecting neighbouring mol­ecules into layers perpendicular to the c axis.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.030
• wR factor = 0.083
• Data-to-parameter ratio = 20.0

checkCIF/PLATON results

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S1. Comment

Nitro­gen containing heteroaromatic systems like pyridines are some of the most investigated organic compounds primarily because of their importance in the pharmaceutical and chemical industries. Pyridine derivatives have been widely studied in analytical chemistry as an acid-base, redox and biomedical agent and for their photo-physical properties. A common synthetic pyridine derivative is 2-(phenyl­diazenyl)pyridine (Krause & Krause, 1980). This compound is a well known ligand with a basic nitro­gen atom on the pyridine ring able to coordinate to transition metal complexes. It has various applications, for example as a chemotherapeutic drug (Wong & Giandomenico, 1999), it has anti­cancer properties (Wu et al., 2006; Hotze et al., 2004; Velder et al., 2000) and is active in catalysing the epoxidation of olefins (Barf & Sheldon 1995). Coordination compounds of Zn^II incorporating the diazenyl moiety were shown to have photochromic properties (Saha et al., 2014; Dutta et al., 2014; Datta et al., 2014) as well as non-linear optical properties, which were investigated for the storage of optical information (Zhang et al., 2012).

We here report the preparation and crystal structure of a new Zn^II complex with the well known diazenyl­pyridine ligand 2-(phenyl­diazenyl)pyridine (C₁₁H₉N₃), or azpy. The molecular structure of the title complex, [Zn(C₁₁H₉N₃)₂Cl₂], is slightly distorted tetra­hedral as illustrated in Fig.1. The Zn atom is four coordinated by two azpy ligands via two N(pyridine) atoms [Zn1—N1 and Zn1—N1ⁱ = 2.0618 (15) Å] and two Cl^- ions [Zn1—Cl1 and Zn1—Cl1ⁱ = 2.2472 (5) Å ; (i): -x+2,y,-z+3/2]. These values compare well with those of other related di­chloro Zn^II compounds with pyridine ligands, such as [Zn(N,N-di­ethyl-4-[(pyridin-2-yl-kN)diazenyl]aniline)₂Cl₂] (Leesakul et al., 2011) with Zn—N distances of 2.0513 (9) and 2.0439 (19) Å or [Zn(pyridine)₂Cl₂] (Steffen & Palenik, 1976) with Zn —N distances of 2.046 (5) and 2.052 (6) Å. The reported Zn—Cl bond distances in the complex of Leesakul et al. averaged to 2.264 (6) Å, those in [Zn(pyridine)₂Cl₂] (Steffen & Palenik, 1976) averaged to 2.2215 Å, which are thus slightly longer and shorter respectively than those of the title complex [Zn(azpy)₂Cl₂].

The azo (N═N) distance in the Zn^II complex is 1.244 (2) Å, which is comparable to that in the free azpy ligand, 1.248 (4) Å (Panneerselvam et al., 2000), which is expected as the azo nitro­gen of the azpy ligand is not metal coordinated. All N—Zn—Cl, Cl—Zn—Cl and N—Zn—N bond angles deviate somewhat from the ideal from 109.5°, especially for the angle N1—Zn1—N1ⁱ = 124.45 (9)°, probably due to steric demands of the azpy ligand. The torsion angle of the pyridine-azo-phenyl atoms, C5—N2—N3—C6 is 179.59 (15)°. The dihedral angle of the mean planes between the pyridine and the phenyl ring in the ligand molecule is 11.9 (1)°.

S2. Supra­molecular features

Weak intra and inter­molecular C—H···Cl inter­actions (C···Cl = 3.411 (2) and 3.675 (2) Å; see Table 1, Hydrogen-bond geometry) connect neighboring molecules into layers perpendicular to the c-axis (Fig. 2–4).

S3. Experimental

An aceto­nitrile solution (10 mL) of 2-(phenyl­diazenyl)pyridine (azpy) (0.183 g, 1.0 mmol) was added dropwise to zinc(II) chloride (0.068 g, 0.50 mmol), then refluxed for 4 h. After being filtered, the filtrate was left standing overnight at 4°C. Orange crystals were obtained (yield 71.31%, 0.179 g). Anal. Calcd for ZnC₂₂H₁₈N₆Cl₂: C, 52.56; H, 3.61; N, 16.72. Found: C, 52.56; H, 3.55; N, 16.96.

S4. Refinement

All H atoms of aromatic carbon were positioned geometrically and refined as riding atoms with with C—H = 0.93 Å, and with U_eq(H) = 1.2 U_eq(C).

Related literature

For background to diazenylpyridine compounds, see: Krause & Krause (1980). For applications of diazenylpyridine complexes, see: Wong & Giandomenico (1999); Wu et al. (2006); Hotze et al. (2004); Velder et al. (2000); Barf & Sheldon (1995). For applications of zinc–diazenyl complexes, see: Saha et al. (2014); Dutta et al. (2014); Datta et al. (2014); Zhang et al. (2012). For related structures, see: Leesakul et al. (2011), Panneerselvam et al. (2000), and Steffen & Palenik (1976).

Structure description

Nitro­gen containing heteroaromatic systems like pyridines are some of the most investigated organic compounds primarily because of their importance in the pharmaceutical and chemical industries. Pyridine derivatives have been widely studied in analytical chemistry as an acid-base, redox and biomedical agent and for their photo-physical properties. A common synthetic pyridine derivative is 2-(phenyl­diazenyl)pyridine (Krause & Krause, 1980). This compound is a well known ligand with a basic nitro­gen atom on the pyridine ring able to coordinate to transition metal complexes. It has various applications, for example as a chemotherapeutic drug (Wong & Giandomenico, 1999), it has anti­cancer properties (Wu et al., 2006; Hotze et al., 2004; Velder et al., 2000) and is active in catalysing the epoxidation of olefins (Barf & Sheldon 1995). Coordination compounds of Zn^II incorporating the diazenyl moiety were shown to have photochromic properties (Saha et al., 2014; Dutta et al., 2014; Datta et al., 2014) as well as non-linear optical properties, which were investigated for the storage of optical information (Zhang et al., 2012).

We here report the preparation and crystal structure of a new Zn^II complex with the well known diazenyl­pyridine ligand 2-(phenyl­diazenyl)pyridine (C₁₁H₉N₃), or azpy. The molecular structure of the title complex, [Zn(C₁₁H₉N₃)₂Cl₂], is slightly distorted tetra­hedral as illustrated in Fig.1. The Zn atom is four coordinated by two azpy ligands via two N(pyridine) atoms [Zn1—N1 and Zn1—N1ⁱ = 2.0618 (15) Å] and two Cl^- ions [Zn1—Cl1 and Zn1—Cl1ⁱ = 2.2472 (5) Å ; (i): -x+2,y,-z+3/2]. These values compare well with those of other related di­chloro Zn^II compounds with pyridine ligands, such as [Zn(N,N-di­ethyl-4-[(pyridin-2-yl-kN)diazenyl]aniline)₂Cl₂] (Leesakul et al., 2011) with Zn—N distances of 2.0513 (9) and 2.0439 (19) Å or [Zn(pyridine)₂Cl₂] (Steffen & Palenik, 1976) with Zn —N distances of 2.046 (5) and 2.052 (6) Å. The reported Zn—Cl bond distances in the complex of Leesakul et al. averaged to 2.264 (6) Å, those in [Zn(pyridine)₂Cl₂] (Steffen & Palenik, 1976) averaged to 2.2215 Å, which are thus slightly longer and shorter respectively than those of the title complex [Zn(azpy)₂Cl₂].

The azo (N═N) distance in the Zn^II complex is 1.244 (2) Å, which is comparable to that in the free azpy ligand, 1.248 (4) Å (Panneerselvam et al., 2000), which is expected as the azo nitro­gen of the azpy ligand is not metal coordinated. All N—Zn—Cl, Cl—Zn—Cl and N—Zn—N bond angles deviate somewhat from the ideal from 109.5°, especially for the angle N1—Zn1—N1ⁱ = 124.45 (9)°, probably due to steric demands of the azpy ligand. The torsion angle of the pyridine-azo-phenyl atoms, C5—N2—N3—C6 is 179.59 (15)°. The dihedral angle of the mean planes between the pyridine and the phenyl ring in the ligand molecule is 11.9 (1)°.

Weak intra and inter­molecular C—H···Cl inter­actions (C···Cl = 3.411 (2) and 3.675 (2) Å; see Table 1, Hydrogen-bond geometry) connect neighboring molecules into layers perpendicular to the c-axis (Fig. 2–4).

An aceto­nitrile solution (10 mL) of 2-(phenyl­diazenyl)pyridine (azpy) (0.183 g, 1.0 mmol) was added dropwise to zinc(II) chloride (0.068 g, 0.50 mmol), then refluxed for 4 h. After being filtered, the filtrate was left standing overnight at 4°C. Orange crystals were obtained (yield 71.31%, 0.179 g). Anal. Calcd for ZnC₂₂H₁₈N₆Cl₂: C, 52.56; H, 3.61; N, 16.72. Found: C, 52.56; H, 3.55; N, 16.96.

For background to diazenylpyridine compounds, see: Krause & Krause (1980). For applications of diazenylpyridine complexes, see: Wong & Giandomenico (1999); Wu et al. (2006); Hotze et al. (2004); Velder et al. (2000); Barf & Sheldon (1995). For applications of zinc–diazenyl complexes, see: Saha et al. (2014); Dutta et al. (2014); Datta et al. (2014); Zhang et al. (2012). For related structures, see: Leesakul et al. (2011), Panneerselvam et al. (2000), and Steffen & Palenik (1976).

Refinement details

All H atoms of aromatic carbon were positioned geometrically and refined as riding atoms with with C—H = 0.93 Å, and with U_eq(H) = 1.2 U_eq(C).

Computing details

Data collection: SMART (Bruker, 2013); cell refinement: SAINT (Bruker, 2013); data reduction: SAINT (Bruker, 2013); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: WinGX (Farrugia, 2012) and publCIF (Westrip, 2010).

Figures

	Fig. 1. Molecular structure of [Zn(C11H9N3)2Cl2] with thermal ellipsoids plotted at the 30% probability level. Non-labelled atoms are created by the twofold symmetry axis [symmetry operator: (i) -x + 2, y, -z + 3/2].
	Fig. 2. Two–dimensional interaction sheet of [Zn(C11H9N3)2Cl2] plotted down c, formed through weak C–H···Cl interactions.
	Fig. 3. Two–dimensional interaction sheet of [Zn(C11H9N3)2Cl2] plotted down b axis, formed through weak C–H···Cl interactions.
	Fig. 4. The arrangement of two-dimensional layers plotted down the a axis showing a lateral view of alternating C···Cl contact directions of adjacent sheets (A and B layers). H atoms are omitted for clarity.

Dichloridobis[2-(phenyldiazenyl)pyridine-κN¹]zinc

Crystal data

[ZnCl2(C11H9N3)2]	Dx = 1.472 Mg m^−3
Mr = 502.69	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbcn	Cell parameters from 9900 reflections
a = 13.7960 (4) Å	θ = 3.2–28.2°
b = 10.1905 (3) Å	µ = 1.34 mm^−1
c = 16.1305 (5) Å	T = 298 K
V = 2267.76 (12) Å^3	Block, orange
Z = 4	0.36 × 0.32 × 0.30 mm
F(000) = 1024

Data collection

Bruker APEXII CCD diffractometer	2160 reflections with I > 2σ(I)
φ and ω scans	Rint = 0.041
Absorption correction: multi-scan (SADABS; Bruker, 2013)	θmax = 28.3°, θmin = 3.5°
Tmin = 0.708, Tmax = 0.746	h = −18→18
65168 measured reflections	k = −13→13
2820 independent reflections	l = −21→21

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.030	H-atom parameters constrained
wR(F^2) = 0.083	w = 1/[σ^2(Fo^2) + (0.0384P)^2 + 0.7794P] where P = (Fo^2 + 2Fc^2)/3
S = 1.06	(Δ/σ)max = 0.001
2820 reflections	Δρmax = 0.35 e Å^−3
141 parameters	Δρmin = −0.22 e Å^−3

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Zn1	1.0000	0.21091 (3)	0.7500	0.04573 (11)
Cl1	0.96785 (4)	0.08709 (5)	0.63805 (3)	0.06114 (15)
N1	0.86977 (11)	0.30520 (15)	0.76959 (10)	0.0468 (3)
N2	0.95560 (12)	0.45206 (15)	0.84789 (10)	0.0514 (4)
N3	0.95301 (13)	0.55766 (16)	0.88646 (11)	0.0584 (4)
C1	0.78854 (15)	0.2566 (2)	0.73676 (13)	0.0571 (5)
H1	0.7927	0.1832	0.7026	0.069*
C2	0.69884 (17)	0.3110 (2)	0.75155 (14)	0.0676 (6)
H2	0.6434	0.2755	0.7275	0.081*
C3	0.69288 (16)	0.4185 (2)	0.80247 (16)	0.0730 (6)
H3	0.6330	0.4563	0.8140	0.088*
C4	0.77541 (15)	0.4698 (2)	0.83614 (14)	0.0627 (5)
H4	0.7726	0.5429	0.8706	0.075*
C5	0.86318 (13)	0.41115 (18)	0.81815 (11)	0.0484 (4)
C6	1.04406 (15)	0.60029 (19)	0.91730 (12)	0.0555 (5)
C7	1.04401 (19)	0.7222 (2)	0.95484 (16)	0.0696 (6)
H7	0.9866	0.7696	0.9593	0.084*
C8	1.1291 (2)	0.7733 (3)	0.98561 (16)	0.0789 (7)
H8	1.1293	0.8553	1.0110	0.095*
C9	1.2132 (2)	0.7037 (3)	0.97888 (15)	0.0763 (7)
H9	1.2707	0.7390	0.9990	0.092*
C10	1.21338 (17)	0.5810 (2)	0.94239 (14)	0.0706 (6)
H10	1.2709	0.5338	0.9386	0.085*
C11	1.12915 (16)	0.5283 (2)	0.91168 (13)	0.0623 (5)
H11	1.1291	0.4455	0.8874	0.075*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.03382 (16)	0.04842 (18)	0.05494 (19)	0.000	0.00041 (11)	0.000
Cl1	0.0475 (3)	0.0725 (3)	0.0635 (3)	0.0004 (2)	−0.0018 (2)	−0.0153 (2)
N1	0.0390 (8)	0.0491 (8)	0.0522 (8)	0.0044 (6)	0.0020 (6)	0.0048 (6)
N2	0.0533 (9)	0.0493 (8)	0.0518 (9)	0.0059 (7)	0.0038 (7)	0.0004 (7)
N3	0.0597 (11)	0.0517 (9)	0.0638 (10)	0.0067 (8)	0.0061 (8)	−0.0026 (8)
C1	0.0431 (10)	0.0613 (11)	0.0669 (13)	0.0021 (9)	−0.0025 (8)	0.0013 (9)
C2	0.0393 (10)	0.0797 (15)	0.0837 (16)	0.0077 (10)	−0.0056 (10)	0.0097 (12)
C3	0.0490 (12)	0.0840 (16)	0.0861 (16)	0.0254 (11)	0.0070 (11)	0.0133 (13)
C4	0.0602 (12)	0.0615 (12)	0.0663 (12)	0.0211 (10)	0.0057 (10)	0.0027 (10)
C5	0.0472 (10)	0.0497 (10)	0.0483 (10)	0.0089 (8)	0.0034 (8)	0.0093 (8)
C6	0.0584 (12)	0.0551 (11)	0.0530 (11)	0.0001 (9)	0.0074 (9)	0.0013 (9)
C7	0.0696 (14)	0.0602 (13)	0.0790 (15)	0.0002 (10)	0.0151 (12)	−0.0122 (11)
C8	0.0851 (18)	0.0683 (15)	0.0832 (16)	−0.0170 (13)	0.0133 (14)	−0.0153 (12)
C9	0.0742 (16)	0.0856 (17)	0.0690 (14)	−0.0211 (13)	0.0029 (12)	0.0037 (12)
C10	0.0624 (13)	0.0789 (16)	0.0704 (14)	0.0030 (11)	0.0025 (11)	0.0065 (12)
C11	0.0657 (13)	0.0609 (12)	0.0602 (12)	0.0051 (10)	0.0035 (10)	−0.0020 (10)

Geometric parameters (Å, º)

Zn1—N1	2.0618 (15)	C3—H3	0.9300
Zn1—N1^i	2.0619 (15)	C4—C5	1.381 (3)
Zn1—Cl1^i	2.2471 (5)	C4—H4	0.9300
Zn1—Cl1	2.2472 (5)	C6—C7	1.382 (3)
N1—C1	1.335 (3)	C6—C11	1.387 (3)
N1—C5	1.337 (2)	C7—C8	1.377 (3)
N2—N3	1.244 (2)	C7—H7	0.9300
N2—C5	1.425 (2)	C8—C9	1.364 (4)
N3—C6	1.419 (3)	C8—H8	0.9300
C1—C2	1.377 (3)	C9—C10	1.382 (3)
C1—H1	0.9300	C9—H9	0.9300
C2—C3	1.372 (3)	C10—C11	1.372 (3)
C2—H2	0.9300	C10—H10	0.9300
C3—C4	1.365 (3)	C11—H11	0.9300
N1—Zn1—N1^i	124.45 (9)	C5—C4—H4	120.6
N1—Zn1—Cl1^i	108.09 (4)	N1—C5—C4	122.15 (19)
N1^i—Zn1—Cl1^i	102.29 (5)	N1—C5—N2	111.89 (15)
N1—Zn1—Cl1	102.29 (5)	C4—C5—N2	125.96 (18)
N1^i—Zn1—Cl1	108.09 (4)	C7—C6—C11	120.3 (2)
Cl1^i—Zn1—Cl1	111.68 (3)	C7—C6—N3	115.36 (19)
C1—N1—C5	118.37 (17)	C11—C6—N3	124.36 (19)
C1—N1—Zn1	119.85 (13)	C8—C7—C6	119.8 (2)
C5—N1—Zn1	121.69 (13)	C8—C7—H7	120.1
N3—N2—C5	113.33 (16)	C6—C7—H7	120.1
N2—N3—C6	114.51 (17)	C9—C8—C7	120.0 (2)
N1—C1—C2	122.4 (2)	C9—C8—H8	120.0
N1—C1—H1	118.8	C7—C8—H8	120.0
C2—C1—H1	118.8	C8—C9—C10	120.4 (2)
C3—C2—C1	118.6 (2)	C8—C9—H9	119.8
C3—C2—H2	120.7	C10—C9—H9	119.8
C1—C2—H2	120.7	C11—C10—C9	120.4 (2)
C4—C3—C2	119.6 (2)	C11—C10—H10	119.8
C4—C3—H3	120.2	C9—C10—H10	119.8
C2—C3—H3	120.2	C10—C11—C6	119.1 (2)
C3—C4—C5	118.8 (2)	C10—C11—H11	120.5
C3—C4—H4	120.6	C6—C11—H11	120.5
C5—N2—N3—C6	179.59 (15)	N3—N2—C5—N1	173.32 (16)
C5—N1—C1—C2	−0.4 (3)	N3—N2—C5—C4	−7.2 (3)
Zn1—N1—C1—C2	176.25 (16)	N2—N3—C6—C7	175.28 (19)
N1—C1—C2—C3	−0.5 (3)	N2—N3—C6—C11	−4.7 (3)
C1—C2—C3—C4	0.9 (3)	C11—C6—C7—C8	1.0 (3)
C2—C3—C4—C5	−0.3 (3)	N3—C6—C7—C8	−179.0 (2)
C1—N1—C5—C4	1.0 (3)	C6—C7—C8—C9	0.1 (4)
Zn1—N1—C5—C4	−175.57 (14)	C7—C8—C9—C10	−1.0 (4)
C1—N1—C5—N2	−179.50 (16)	C8—C9—C10—C11	0.7 (4)
Zn1—N1—C5—N2	3.9 (2)	C9—C10—C11—C6	0.4 (3)
C3—C4—C5—N1	−0.7 (3)	C7—C6—C11—C10	−1.3 (3)
C3—C4—C5—N2	179.92 (19)	N3—C6—C11—C10	178.7 (2)

Symmetry code: (i) −x+2, y, −z+3/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3···Cl1^ii	0.93	2.75	3.675 (2)	173
C1—H1···Cl1	0.93	2.81	3.411 (2)	124

Symmetry code: (ii) x−1/2, y+1/2, −z+3/2.