Diaqua­(6-bromo­picolinato-κ²N,O)(nitrato-κ²O,O)copper(II)

In the monomeric title complex, [Cu(C₆H₃BrNO₂)(NO₃)(H₂O)₂], the Cu^II ion is coordinated by a bidentate 6-bromo­picolinate ion, one nitrate ion and two water mol­ecules in a geometry inter­mediate between five- and six-coordinate. Conventional O—H...O hydrogen bonds link the complex mol­ecules, forming layers parallel to the ab plane.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.038
• wR factor = 0.137
• Data-to-parameter ratio = 19.5

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT919_ALERT_3_B Reflection # Likely Affected by the Beamstop ...          2
PLAT934_ALERT_3_B Number of (Iobs-Icalc)/SigmaW .gt. 10 Outliers .          3

Alert level C
PLAT241_ALERT_2_C Check High      Ueq as Compared to Neighbors for         O4
PLAT431_ALERT_2_C Short Inter HL..A Contact  Br1    ..  O2      ..       3.07 Ang.
PLAT918_ALERT_3_C Reflection(s) # with I(obs) much smaller I(calc)          2
PLAT912_ALERT_4_C Missing # of FCF Reflections Above STh/L=  0.600        342

Alert level G
PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints .......          7
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported   _diffrn_ambient_temperature        293 K
PLAT794_ALERT_5_G Note: Tentative Bond Valency for Cu1     .......       2.14

   0 ALERT level A = In general: serious problem
   2 ALERT level B = Potentially serious problem
   4 ALERT level C = Check and explain
   4 ALERT level G = General alerts; check

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   2 ALERT type 2 Indicator that the structure model may be wrong or deficient
   4 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

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S1. Comment

The title compound was obtained within a project of synthesizing new molecular magnets (Martins, Silva et al., 2008; Martins, Ramos Silva et al., 2008; Ramos Silva et al., 2001a, 2001b, 2001c, 2005a, 2005b). Molecular based magnets can capitalize on the flexibility inherent in carbon chemistry. Such flexibility allows a rational choice of ligands to control the dimensionality of the system, so that quantum effects can be enhanced. Picolinic and hydroxypicolinic acid have been widely used as ligands in low- dimensional metallic systems (Eppley et al., 1997) but 6-bromopicolinic acid has been scarcely used. A different substituent in the pyridine ring may lead to significant electronic and steric effects enlarging the structural diversity. In fact, Kukovec et al. (2008) synthesized a copper (II) complex with 6-bromopicolinic acid as a bidentate ligand in which the magnetic exchange pathway is connected to the Br···π interaction.

In the title compound, the Cu^II ion is coordinated by a bromopicolinate ligand, two water molecules and a nitrate ion (Fig. 1). One of the Cu—O bonds is rather long [Cu1—O4 2.682 (3) °] so that the coordination about the copper ion is intermediate between five and six-coordination. If the latter bond is to be ignored, the remaining coordination stereochemistry is near a square pyramid. In that case, the copper ion is 0.3149 (5) Å above the least-squares plane of the basal coordinating atoms. The H-bond network is confined to layers parallel to the ab plane (Fig. 2, Table 1). The bromine also forms a short contact [3.066 (2) Å] with O2ⁱ [symmetry code: (i) -1 + x,y,z].

The magnetic susceptibility was measured using a SQUID magnetometer in function of temperature with an applied magnetic field of 2 T. The inverse susceptibility showed a linear dependence with temperature, excluding any interaction between magnetic centers.

Related literature

For general background to copper complexes with low-dimensional elements synthesized by our group, see: Martins, Ramos Silva et al. (2008), Martins, Silva et al. (2008); Ramos Silva et al. (2001a,b,c, 2005a,b). For a magnetic low-dimensional system with picolinic acid, see: Eppley et al. (1997). For a similar compound with magnetic properties, see: Kukovec et al. (2008).

S2. Experimental

0.14 mmol of 6-bromo-2-pyridinecarboxaldehyde in dichloromethane (10 ml) was added to 0.12 mmol of Cu(NO3)2.3H2O in water (10 ml). After a few weeks, blue single crystals of the title compound were obtained.

S3. Refinement

H atoms bound to C atoms were placed at calculated positions and were treated as riding on the parent atoms with C—H = 0.93 Å (aromatic) and with U_iso(H) = 1.2 U_eq(C). H atoms of water molecules O6 an O7 could not be correctly located in a difference Fourier map. They were placed at positions calculated to optimize H-bonds and refined using restraints [O—H = 0.85 (1) Å, H—H = 1.34 (1) Å] and U_iso(H) = 1.5Ueq(O). To avoid that water (O6) H atoms slip into density peaks around the heavy metal atom, a DFIX command was used to garantee a Cu···H distance of at least 2.50 (1) Å. There are maximum and minimum density peaks slightly above 1 e/ų.

Computing details

Data collection: SMART (Bruker, 2003); cell refinement: SAINT (Bruker, 2003); data reduction: SAINT (Bruker, 2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. ORTEPII (Johnson, 1976) plot of the title compound. Displacement ellipsoids are drawn at the 50% level.
	Fig. 2. Packing of the molecules in the unit cell showing the H-bonds as dashed lines.

Diaqua(6-bromopicolinato-κ²N,O)(nitrato- κ²O,O)copper(II)

Crystal data

[Cu(C6H3BrNO2)(NO3)(H2O)2]	F(000) = 1416
Mr = 362.59	Dx = 2.202 Mg m^−3
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 6959 reflections
a = 9.0791 (14) Å	θ = 2.9–26.3°
b = 14.035 (2) Å	µ = 5.68 mm^−1
c = 17.165 (2) Å	T = 293 K
V = 2187.2 (6) Å^3	Needle, blue
Z = 8	0.40 × 0.10 × 0.08 mm

Data collection

Bruker APEX CCD area-detector diffractometer	3263 independent reflections
Radiation source: fine-focus sealed tube	1849 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.069
ϕ and ω scans	θmax = 31.4°, θmin = 2.4°
Absorption correction: multi-scan (SADABS; Sheldrick, 2000)	h = −12→11
Tmin = 0.619, Tmax = 0.999	k = −19→20
35919 measured reflections	l = −24→24

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.038	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.137	w = 1/[σ^2(Fo^2) + (0.0722P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.03	(Δ/σ)max = 0.001
3263 reflections	Δρmax = 1.06 e Å^−3
167 parameters	Δρmin = −1.19 e Å^−3
7 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0019 (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.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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

	x	y	z	Uiso*/Ueq
Cu1	0.27639 (5)	0.10769 (4)	0.67505 (3)	0.03377 (16)
Br1	−0.01236 (4)	0.12831 (4)	0.52718 (3)	0.04471 (16)
C1	0.5394 (5)	0.1362 (3)	0.6017 (2)	0.0356 (10)
C2	0.4323 (4)	0.1249 (2)	0.5356 (2)	0.0291 (8)
C3	0.4765 (5)	0.1207 (4)	0.4602 (3)	0.0463 (12)
H3	0.5763	0.1214	0.4479	0.056*
C4	0.3723 (6)	0.1155 (4)	0.4020 (3)	0.0542 (14)
H4	0.4004	0.1107	0.3500	0.065*
C5	0.2261 (5)	0.1175 (4)	0.4223 (3)	0.0500 (13)
H5	0.1533	0.1164	0.3843	0.060*
C6	0.1890 (5)	0.1212 (3)	0.5006 (2)	0.0367 (10)
O1	0.4821 (3)	0.1405 (2)	0.66941 (16)	0.0406 (8)
O2	0.6707 (3)	0.1410 (3)	0.58800 (18)	0.0529 (9)
O3	0.1019 (3)	0.0189 (2)	0.67729 (14)	0.0378 (7)
O4	0.2795 (3)	−0.0834 (3)	0.66960 (18)	0.0516 (9)
O5	0.0612 (4)	−0.1309 (2)	0.7005 (2)	0.0572 (9)
O6	0.3112 (3)	0.0737 (3)	0.78475 (15)	0.0505 (9)
H6A	0.3992 (12)	0.074 (3)	0.8019 (8)	0.076*
H6B	0.264 (3)	0.103 (2)	0.8203 (5)	0.076*
O7	0.1350 (4)	0.2239 (2)	0.70395 (19)	0.0494 (8)
H7A	0.156 (5)	0.2826 (10)	0.703 (3)	0.074*
H7B	0.086 (4)	0.222 (4)	0.7459 (14)	0.074*
N1	0.2882 (4)	0.1232 (2)	0.55771 (19)	0.0313 (8)
N2	0.1477 (4)	−0.0683 (3)	0.68317 (17)	0.0356 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0240 (3)	0.0461 (4)	0.0312 (2)	0.0008 (2)	0.00166 (17)	0.0011 (2)
Br1	0.0287 (2)	0.0573 (3)	0.0481 (3)	0.00161 (19)	−0.00589 (16)	0.0033 (2)
C1	0.030 (2)	0.040 (3)	0.037 (2)	−0.0019 (18)	−0.0022 (16)	0.0035 (17)
C2	0.028 (2)	0.022 (2)	0.0374 (19)	0.0017 (16)	0.0021 (15)	0.0012 (15)
C3	0.035 (3)	0.063 (3)	0.041 (2)	−0.002 (2)	0.0043 (17)	−0.001 (2)
C4	0.049 (3)	0.079 (4)	0.035 (2)	−0.004 (2)	0.0032 (19)	−0.007 (2)
C5	0.043 (3)	0.070 (4)	0.037 (2)	−0.004 (2)	−0.0053 (18)	0.002 (2)
C6	0.032 (2)	0.045 (3)	0.0328 (19)	0.0002 (17)	−0.0041 (16)	0.0018 (17)
O1	0.0272 (15)	0.064 (2)	0.0312 (14)	−0.0077 (14)	0.0003 (10)	−0.0009 (13)
O2	0.0238 (16)	0.091 (3)	0.0443 (17)	−0.0025 (15)	0.0015 (12)	0.0099 (16)
O3	0.0269 (14)	0.0397 (19)	0.0468 (15)	0.0008 (12)	−0.0003 (11)	0.0047 (12)
O4	0.0397 (19)	0.049 (2)	0.066 (2)	0.0137 (15)	0.0097 (14)	0.0014 (16)
O5	0.055 (2)	0.052 (2)	0.065 (2)	−0.0217 (17)	−0.0069 (17)	0.0160 (16)
O6	0.0313 (16)	0.087 (3)	0.0326 (14)	0.0088 (16)	0.0015 (11)	0.0027 (16)
O7	0.0525 (19)	0.0418 (19)	0.0541 (17)	0.0043 (16)	0.0184 (14)	−0.0001 (16)
N1	0.0277 (17)	0.032 (2)	0.0340 (16)	−0.0022 (14)	0.0002 (13)	0.0037 (13)
N2	0.037 (2)	0.036 (2)	0.0337 (16)	0.0017 (17)	−0.0030 (14)	0.0025 (14)

Geometric parameters (Å, º)

Cu1—O1	1.926 (3)	C4—C5	1.373 (7)
Cu1—O6	1.968 (3)	C4—H4	0.9300
Cu1—O3	2.016 (3)	C5—C6	1.386 (6)
Cu1—N1	2.029 (3)	C5—H5	0.9300
Cu1—O7	2.134 (3)	C6—N1	1.332 (5)
Br1—C6	1.886 (4)	O3—N2	1.296 (4)
C1—O2	1.218 (5)	O4—N2	1.238 (4)
C1—O1	1.274 (5)	O5—N2	1.215 (5)
C1—C2	1.503 (6)	O6—H6A	0.851 (9)
C2—C3	1.356 (6)	O6—H6B	0.85 (2)
C2—N1	1.363 (5)	O7—H7A	0.845 (10)
C3—C4	1.378 (6)	O7—H7B	0.85 (3)
C3—H3	0.9300
O1—Cu1—O6	87.13 (12)	C3—C4—H4	120.7
O1—Cu1—O3	155.59 (13)	C4—C5—C6	118.9 (4)
O6—Cu1—O3	87.61 (12)	C4—C5—H5	120.6
O1—Cu1—N1	82.72 (12)	C6—C5—H5	120.6
O6—Cu1—N1	165.35 (13)	N1—C6—C5	123.3 (4)
O3—Cu1—N1	97.29 (11)	N1—C6—Br1	118.4 (3)
O1—Cu1—O7	114.35 (14)	C5—C6—Br1	118.2 (3)
O6—Cu1—O7	93.40 (13)	C1—O1—Cu1	115.5 (3)
O3—Cu1—O7	89.74 (13)	N2—O3—Cu1	109.4 (2)
N1—Cu1—O7	100.38 (13)	Cu1—O6—H6A	118.7 (11)
O2—C1—O1	125.0 (4)	Cu1—O6—H6B	118.9 (11)
O2—C1—C2	119.6 (4)	H6A—O6—H6B	103.2 (14)
O1—C1—C2	115.5 (4)	Cu1—O7—H7A	127 (3)
C3—C2—N1	123.3 (4)	Cu1—O7—H7B	119 (3)
C3—C2—C1	122.3 (4)	H7A—O7—H7B	99 (4)
N1—C2—C1	114.3 (3)	C6—N1—C2	116.4 (3)
C2—C3—C4	119.4 (4)	C6—N1—Cu1	133.9 (3)
C2—C3—H3	120.3	C2—N1—Cu1	109.2 (2)
C4—C3—H3	120.3	O5—N2—O4	123.1 (4)
C5—C4—C3	118.6 (4)	O5—N2—O3	119.7 (4)
C5—C4—H4	120.7	O4—N2—O3	117.2 (3)
O2—C1—C2—C3	−0.6 (6)	O7—Cu1—O3—N2	−162.2 (2)
O1—C1—C2—C3	179.0 (4)	C5—C6—N1—C2	2.3 (6)
O2—C1—C2—N1	−178.1 (4)	Br1—C6—N1—C2	−175.4 (3)
O1—C1—C2—N1	1.5 (5)	C5—C6—N1—Cu1	−168.5 (3)
N1—C2—C3—C4	0.7 (7)	Br1—C6—N1—Cu1	13.8 (5)
C1—C2—C3—C4	−176.6 (4)	C3—C2—N1—C6	−2.8 (6)
C2—C3—C4—C5	1.9 (7)	C1—C2—N1—C6	174.7 (3)
C3—C4—C5—C6	−2.3 (7)	C3—C2—N1—Cu1	170.2 (3)
C4—C5—C6—N1	0.2 (7)	C1—C2—N1—Cu1	−12.3 (4)
C4—C5—C6—Br1	177.9 (4)	O1—Cu1—N1—C6	−174.5 (4)
O2—C1—O1—Cu1	−169.1 (4)	O6—Cu1—N1—C6	139.0 (5)
C2—C1—O1—Cu1	11.3 (5)	O3—Cu1—N1—C6	30.1 (4)
O6—Cu1—O1—C1	155.0 (3)	O7—Cu1—N1—C6	−60.9 (4)
O3—Cu1—O1—C1	77.1 (4)	O1—Cu1—N1—C2	14.3 (2)
N1—Cu1—O1—C1	−14.5 (3)	O6—Cu1—N1—C2	−32.2 (6)
O7—Cu1—O1—C1	−112.6 (3)	O3—Cu1—N1—C2	−141.1 (2)
O1—Cu1—O3—N2	8.9 (4)	O7—Cu1—N1—C2	127.8 (2)
O6—Cu1—O3—N2	−68.8 (2)	Cu1—O3—N2—O5	165.8 (3)
N1—Cu1—O3—N2	97.3 (2)	Cu1—O3—N2—O4	−15.0 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O6—H6A···O3^i	0.85 (1)	2.03 (2)	2.825 (4)	156 (4)
O6—H6B···O2^ii	0.85 (2)	1.86 (1)	2.700 (4)	166 (2)
O7—H7A···O4^iii	0.85 (1)	2.06 (2)	2.874 (5)	163 (5)
O7—H7B···O1^ii	0.85 (3)	2.08 (3)	2.833 (4)	148 (5)

Symmetry codes: (i) x+1/2, y, −z+3/2; (ii) x−1/2, y, −z+3/2; (iii) −x+1/2, y+1/2, z.