One-dimensional self-assembly of bis­(3-benzyl­pentane-2,4-dionato)copper(II) in the solid state, mediated by weak C—H...O hydrogen bonding

In the title complex, [Cu(C₁₂H₁₃O₂)₂], the copper(II) ion lies on a crystallographic centre of symmetry and exhibits a square-planar coordination environment formed by four O atoms of two chelate β-diketonate ligands. The nearest neighbours of the copper(II) ion in the apical direction are two α-C atoms of β-diketonate ligands, 3.263 (2) Å away from the metal ion. Mol­ecules in the crystal are stacked face-to-face and held together by weak C—H...O hydrogen bonding and π–π stacking inter­actions.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.030
• wR factor = 0.088
• Data-to-parameter ratio = 17.0

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT063_ALERT_3_C Crystal Probably too Large for Beam Size .......       0.80 mm
PLAT199_ALERT_1_C Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_C Check the Reported _diffrn_ambient_temperature .        293 K
PLAT480_ALERT_4_C Long H...A H-Bond Reported H1B    ..  O1      ..       2.79 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H5C    ..  O2      ..       2.88 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H6B    ..  O1      ..       2.78 Ang.
PLAT481_ALERT_4_C Long D...A H-Bond Reported C5     ..  O2      ..       3.73 Ang.

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

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

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S1. Comment

Copper(II) β-diketonate molecules are often planar and coordinationaly unsaturated. As a means to achieve coordination saturation the molecules readily self-assemble by way of weak intermolecular forces. Oligomers and polymers that form in such a way exhibit physical and chemical properties that render the compounds interesting in the context of materials science (Soldatov et al., 2003).

As a part of a study on the effects of weak interactions on the self-assembly properties of copper(II) β-diketonates, a series of β-diketonate ligands carrying sterically demanding groups in the α-position was prepared, including 3-benzylpentane-2,4-dione, H(αBzl)acac (Judaš & Kaitner, 2005).

In this paper we report the crystal and molecular structure of bis(3-benzylpentane-2,4-dionato)copper(II), Cu[(αBzl)acac]₂, (I).

In the Cu[(αBzl)acac]₂ complex molecule, which possesses a crystallographically imposed center of symmetry (Fig. 1), four O atoms of two β-diketonato ligands surround the copper(II) ion to form a coordination environment that is square-planar by symmetry. The six-membered chelate rings are folded at an angle of 2.5 (3)° about the O1···O2 line. The phenyl ring of the benzyl substituent is almost perpendicular to the chelate mean plane [dihedral angle 81.333 (6)°]. The significant distortion of the tetrahedral angle around atom C6, reflected in the value of the C3—C6—C7 angle of 114.06 (15)°, is most probably caused by the effects of molecular packing rather than intramolecular steric hindrances.

Molecules are linked together in the crystal by several weak cooperative C—H···O hydrogen bonds (Table 1). Specifically, the C1···O1ⁱ and C5···O2ⁱ hydrogen bonds [symmetry code: (i) 1 + x, y, z] are responsible for the bending of the carbon backbone of the molecule (Fig. 2), so as to tilt the atoms C1 and C5 out of the plane defined by atoms C2, C3, C4, O1, O2 and Cu by 0.142 (4) and 0.165 (4) Å, respectively.

The molecules in the crystal exhibit significant π–π stacking interactions involving chelate rings. In summary, self-assembly of copper complex molecules through C–H···O hydrogen bond and π–π stacking forces link the molecules into one-dimensional ribbons running parallel to the a axis (Fig. 3).

The comparison of crystal and molecular structures of the title compound and its analog bis(pentane-2,4-dionato)copper(II) (Starikova & Shugam, 1969; Lebrun et al., 1986) suggests that the introduction of a bulky benzyl substituent at the α-position of the ligand affects more the crystal than the molecular structure of the bis(chelato)copper(II) complex.

S2. Experimental

The ligand 3-benzylpentane-2,4-dione was prepared from sodium acetylacetonate and benzyl bromide by a previously described method (Morgan & Taylor, 1925) as a yellow oil. The title compound was prepared by the reaction of freshly prepared 3-benzylpentane-2,4-dione with copper(II) acetate in ethanol using triethylamine as a catalyst. Specifically, copper(II) acetate monohydrate (0.25 g, 1.3 mmol) was dissolved in hot ethanol (35 ml) containing a few drops of triethylamine. The ligand solution was prepared separately by dissolving 3-benzylpentane-2,4-dione (0.50 g, 2.6 mmol) in ethanol (10 ml). The hot solution of the ligand was added dropwise to the stirred hot solution of copper(II) acetate and catalyst until a precipitate of metallic gray colour separated. The solid was filtered off by suction and washed with one portion of cold ethanol, one portion of distiled water and one more portion of cold ethanol. The product was dried and recrystallized from benzene (yield 71%). Single crystals of the title compound were prepared by diffusion method. A warm ethanol solution (328 K) of the complex was overlayed with n-hexane (5 ml) to yield long and fragile needles of Cu[(αBzl)acac]₂. Thermal analyses (TG and DSC) of purified Cu[(αBzl)acac]₂ were performed using Mettler thermal analysis modules. The complex compound begins to melt with decomposition at 449 K in oxygen atmosphere. In a nitrogen atmosphere the complex melts at 482 K, ΔH_fus = 47.3 kJ mol⁻¹.

S3. Refinement

Coordinates of H atoms bonded to C atoms were calculated following the stereochemical rules with C—H distances of 0.93 Å for phenyl, 0.97 Å for methylene and 0.96 Å for methyl groups. The H atoms were included in the refinement using the riding-model approximation. U_iso(H) were defined as 1.2U_eq of the parent C atoms for phenyl and methylene residues and 1.5U_eq of the parent C atoms for the methyl groups.

Computing details

Data collection: STADI4 (Stoe & Cie, 1995); cell refinement: STADI4; data reduction: X-RED (Stoe & Cie, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997), Mercury (Bruno et al., 2002), RasTop (Valadon, 2004) and POVRay (Persistence of Vision Pty, 2004); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. View of (I) showing 30% probability displacement ellipsoids. [Symmetry code: (ii) −x, −y, −z.]
	Fig. 2. Crystal packing diagram of (I) showing cooperative C—H···O hydrogen bonding (dashed lines) between the molecules.
	Fig. 3. Self-assembly of molecules of (I) through C—H···O hydrogen-bond and π···π-stacking forces (dashed lines) into one-dimensional ribbons parallel to the a axis.

bis(3-benzylpentane-2,4-dionato)copper(II)

Crystal data

[Cu(C12H13O2)2]	Z = 1
Mr = 441.99	F(000) = 231
Triclinic, P1	Dx = 1.400 Mg m^−3 Dm = 1.38 Mg m^−3 Dm measured by flotation in what?
Hall symbol: -P 1	Melting point: 480 K
a = 4.9124 (13) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.9691 (2) Å	Cell parameters from 40 reflections
c = 11.887 (3) Å	θ = 11–17°
α = 110.970 (14)°	µ = 1.07 mm^−1
β = 99.044 (12)°	T = 293 K
γ = 98.254 (12)°	Needle, black
V = 524.1 (2) Å^3	0.80 × 0.17 × 0.13 mm

Data collection

Philips PW1100 diffractometer	2132 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.026
Planar Graphite monochromator	θmax = 27.0°, θmin = 2.2°
ω scan	h = −6→6
Absorption correction: ψ scan (North et al., 1968)	k = −12→12
Tmin = 0.770, Tmax = 0.867	l = −15→15
4582 measured reflections	4 standard reflections every 60 min
2291 independent reflections	intensity decay: 2.8%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.030	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.088	H-atom parameters constrained
S = 1.11	w = 1/[σ^2(Fo^2) + (0.0507P)^2 + 0.086P] where P = (Fo^2 + 2Fc^2)/3
2291 reflections	(Δ/σ)max < 0.001
135 parameters	Δρmax = 0.35 e Å^−3
0 restraints	Δρmin = −0.37 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.

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
Cu	0	0	0	0.03732 (12)
O1	0.2361 (3)	0.14317 (14)	−0.03318 (12)	0.0417 (3)
O2	0.2634 (3)	0.03449 (14)	0.14820 (12)	0.0425 (3)
C1	0.6190 (5)	0.3141 (2)	−0.0296 (2)	0.0516 (5)
H1A	0.4947	0.2995	−0.1058	0.077*
H1B	0.7926	0.2866	−0.046	0.077*
H1C	0.6575	0.4159	0.0251	0.077*
C2	0.4811 (4)	0.22053 (18)	0.02997 (17)	0.0381 (4)
C3	0.6221 (4)	0.22038 (19)	0.14288 (17)	0.0383 (4)
C4	0.5072 (4)	0.12292 (19)	0.19272 (16)	0.0391 (4)
C5	0.6686 (5)	0.1093 (2)	0.30565 (19)	0.0531 (5)
H5A	0.5481	0.0458	0.3307	0.08*
H5B	0.7311	0.2047	0.3716	0.08*
H5C	0.8293	0.0686	0.2865	0.08*
C6	0.9049 (4)	0.3295 (2)	0.21052 (19)	0.0444 (4)
H6A	1.0032	0.2968	0.2699	0.053*
H6B	1.0197	0.3283	0.1509	0.053*
C7	0.8776 (4)	0.4865 (2)	0.27776 (17)	0.0426 (4)
C8	1.0167 (6)	0.6012 (3)	0.2557 (3)	0.0652 (6)
H8	1.1314	0.5821	0.1991	0.078*
C9	0.9902 (7)	0.7455 (3)	0.3159 (3)	0.0792 (8)
H9	1.0838	0.8209	0.2982	0.095*
C10	0.8274 (7)	0.7757 (3)	0.4005 (3)	0.0725 (7)
H10	0.8107	0.8719	0.4417	0.087*
C11	0.6890 (7)	0.6638 (3)	0.4242 (3)	0.0777 (8)
H11	0.5774	0.6842	0.4821	0.093*
C12	0.7118 (6)	0.5201 (3)	0.3635 (2)	0.0640 (6)
H12	0.6143	0.4452	0.3807	0.077*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu	0.03641 (18)	0.03485 (17)	0.04012 (18)	0.00695 (11)	0.00845 (12)	0.01429 (12)
O1	0.0400 (6)	0.0413 (6)	0.0447 (7)	0.0069 (5)	0.0080 (5)	0.0191 (5)
O2	0.0410 (6)	0.0429 (7)	0.0438 (7)	0.0054 (5)	0.0076 (5)	0.0192 (5)
C1	0.0516 (11)	0.0477 (10)	0.0599 (12)	0.0055 (9)	0.0135 (9)	0.0279 (9)
C2	0.0378 (8)	0.0326 (8)	0.0462 (9)	0.0115 (7)	0.0152 (7)	0.0141 (7)
C3	0.0335 (8)	0.0349 (8)	0.0444 (9)	0.0096 (6)	0.0106 (7)	0.0114 (7)
C4	0.0382 (8)	0.0379 (8)	0.0401 (8)	0.0129 (7)	0.0103 (7)	0.0117 (7)
C5	0.0519 (11)	0.0585 (12)	0.0486 (11)	0.0091 (9)	0.0035 (9)	0.0249 (9)
C6	0.0316 (8)	0.0438 (10)	0.0556 (11)	0.0088 (7)	0.0103 (7)	0.0163 (8)
C7	0.0337 (8)	0.0410 (9)	0.0471 (9)	0.0044 (7)	0.0014 (7)	0.0149 (8)
C8	0.0678 (15)	0.0520 (12)	0.0734 (15)	0.0016 (11)	0.0216 (12)	0.0237 (11)
C9	0.091 (2)	0.0455 (13)	0.092 (2)	−0.0021 (12)	0.0048 (16)	0.0299 (13)
C10	0.0815 (18)	0.0431 (11)	0.0703 (15)	0.0138 (11)	−0.0088 (13)	0.0066 (11)
C11	0.088 (2)	0.0585 (14)	0.0759 (17)	0.0224 (13)	0.0295 (15)	0.0070 (12)
C12	0.0712 (15)	0.0484 (12)	0.0722 (15)	0.0108 (11)	0.0313 (12)	0.0177 (11)

Geometric parameters (Å, º)

Cu—O1	1.8997 (13)	C5—H5C	0.96
Cu—O1^i	1.8997 (13)	C6—C7	1.518 (3)
Cu—O2	1.9022 (13)	C6—H6A	0.97
Cu—O2^i	1.9022 (13)	C6—H6B	0.97
O1—C2	1.281 (2)	C7—C8	1.375 (3)
O2—C4	1.286 (2)	C7—C12	1.382 (3)
C1—C2	1.508 (3)	C8—C9	1.394 (4)
C1—H1A	0.96	C8—H8	0.93
C1—H1B	0.96	C9—C10	1.359 (5)
C1—H1C	0.96	C9—H9	0.93
C2—C3	1.411 (3)	C10—C11	1.362 (4)
C3—C4	1.405 (3)	C10—H10	0.93
C3—C6	1.533 (2)	C11—C12	1.385 (3)
C4—C5	1.509 (3)	C11—H11	0.93
C5—H5A	0.96	C12—H12	0.93
C5—H5B	0.96
O1—Cu—O1^i	180.00 (7)	H5A—C5—H5C	109.5
O1—Cu—O2	91.87 (6)	H5B—C5—H5C	109.5
O1^i—Cu—O2	88.13 (6)	C7—C6—C3	114.06 (15)
O1—Cu—O2^i	88.13 (6)	C7—C6—H6A	108.7
O1^i—Cu—O2^i	91.87 (6)	C3—C6—H6A	108.7
O2—Cu—O2^i	180.00 (6)	C7—C6—H6B	108.7
C2—O1—Cu	127.70 (12)	C3—C6—H6B	108.7
C4—O2—Cu	127.86 (12)	H6A—C6—H6B	107.6
C2—C1—H1A	109.5	C8—C7—C12	117.2 (2)
C2—C1—H1B	109.5	C8—C7—C6	121.35 (19)
H1A—C1—H1B	109.5	C12—C7—C6	121.44 (18)
C2—C1—H1C	109.5	C7—C8—C9	121.8 (2)
H1A—C1—H1C	109.5	C7—C8—H8	119.1
H1B—C1—H1C	109.5	C9—C8—H8	119.1
O1—C2—C3	125.82 (16)	C10—C9—C8	119.8 (2)
O1—C2—C1	113.36 (17)	C10—C9—H9	120.1
C3—C2—C1	120.80 (17)	C8—C9—H9	120.1
C4—C3—C2	121.10 (16)	C9—C10—C11	119.3 (2)
C4—C3—C6	120.47 (16)	C9—C10—H10	120.3
C2—C3—C6	118.43 (16)	C11—C10—H10	120.3
O2—C4—C3	125.44 (17)	C10—C11—C12	121.0 (3)
O2—C4—C5	112.61 (17)	C10—C11—H11	119.5
C3—C4—C5	121.92 (17)	C12—C11—H11	119.5
C4—C5—H5A	109.5	C7—C12—C11	120.8 (2)
C4—C5—H5B	109.5	C7—C12—H12	119.6
H5A—C5—H5B	109.5	C11—C12—H12	119.6
C4—C5—H5C	109.5
O2—Cu—O1—C2	1.87 (15)	C2—C3—C4—C5	173.16 (17)
O2^i—Cu—O1—C2	−178.13 (15)	C6—C3—C4—C5	−6.9 (3)
O1—Cu—O2—C4	−2.20 (15)	C4—C3—C6—C7	−103.5 (2)
O1^i—Cu—O2—C4	177.80 (15)	C2—C3—C6—C7	76.4 (2)
Cu—O1—C2—C3	−3.5 (3)	C3—C6—C7—C8	−125.1 (2)
Cu—O1—C2—C1	174.97 (12)	C3—C6—C7—C12	54.8 (3)
O1—C2—C3—C4	4.7 (3)	C12—C7—C8—C9	−0.7 (4)
C1—C2—C3—C4	−173.65 (17)	C6—C7—C8—C9	179.2 (2)
O1—C2—C3—C6	−175.22 (15)	C7—C8—C9—C10	1.2 (4)
C1—C2—C3—C6	6.4 (2)	C8—C9—C10—C11	−0.8 (5)
Cu—O2—C4—C3	4.2 (3)	C9—C10—C11—C12	0.0 (5)
Cu—O2—C4—C5	−174.19 (12)	C8—C7—C12—C11	−0.1 (4)
C2—C3—C4—O2	−5.1 (3)	C6—C7—C12—C11	180.0 (2)
C6—C3—C4—O2	174.90 (16)	C10—C11—C12—C7	0.5 (5)

Symmetry code: (i) −x, −y, −z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1B···O1^ii	0.96	2.79	3.684 (3)	156
C5—H5C···O2^ii	0.96	2.88	3.734 (3)	149
C6—H6B···O1^ii	0.97	2.78	3.604 (2)	143

Symmetry code: (ii) x+1, y, z.