The chemical preparation, crystal structure and spectroscopic characterization of a novel organic-inorganic hybrid material, bis(4-dimethylaminopyridinium) tetrachlorocuprate, have been reported. This compound crystallizes in the monoclinic system in space group C2/c and cell parameters a = 12.4356 (18), b = 12.0901 (17), c = 14.094 (2) Å, β = 115.303 (2)°, Z = 4 and V = 1915.8 (5) Å 3. In the title salt, (C 7H 11N 2) 2CuCl 4, both 4-dimethylaminopyridinium cations are protonated at their pyridine N atoms. The geometry of the CuCl 2- 4 ions is intermediate between tetrahedral and square planar. The atomic arrangement can be described by an alternation of inorganic layers built up by tetrachlorocuprate anions and organic layers formed by 4-dimethylaminopyridinium cations. The organic layers are located in sandwich between the inorganic layers. The anionic and cationic layers are held together by N-H···Cl and C-H···Cl hydrogen bonds into a three-dimensional network. The individual cations are π-π stacked with their neighbors at a distance of 3.7622 (5) Å. The vibrational absorption bands were identified by infrared spectroscopy and DFT calculations allowed their attribution.
Non-covalent interactions, such as hydrogen bonding and π-π stacking, play a very prominent role in the organization of structural units in both biochemistry and material science [
In connection with studies of the structural aspect of halo-metal anion salts containing pyridine derivatives [
CuCl2∙2H2O (1 mmol; 0.17 g) was added to a 4-dimethylaminopyridine (1 mmol; 0.12 mL) solution dissolved in 15 mL of absolute ethanol. The resulting solution was then acidified with 1 mL concentrated HCl and allowed to evaporate slowly at room temperature. Yellow block crystals were formed after 5 days (yield, 78.7%).
Single crystals were carefully selected under a microscope and mounted on a Mitegen micromesh mount with the help of a trace of mineral oil. X-ray diffraction data were collected at 100 K on a Bruker Smart APEX CCD area-detector diffractometer using the ω scan technique with MoKα radiation (λ = 0.7107 Å). Data were collected, the unit cells determined, and the data integrated and corrected for absorption and other systematic errors using the Apex2 suite of programs [
The IR spectrum was recorded in the range 4000 - 400 cm−1 with a “Perkin-Elmer FTIR-1000” spectrometer using samples dispersed in spectroscopically pure KBr pressed into a pellet.
The infrared spectrum was calculated with the Gaussian 09 software by assuming that in the 500 - 4000 cm−1 range all bands were due to the cation. The positions of the protons were optimized at the B3LYP/6-311++G** level of theory and the infrared spectrum was then calculated with the same method. No imaginary frequency was found showing the accuracy of these calculations. For plotting the spectrum a line broadening of 10 cm−1 was applied.
The structure of the title compound consists of discrete
Crystal data | |
---|---|
Chemical formula | 2(C7H11N2)・Cl4Cu |
Mr | 451.70 |
Crystal system, space group | Monoclinic, ˚C 2/c |
Temperature (K) | 100 |
a, b, c (Å) | 12.4356 (18), 12.0901 (17), 14.094 (2) |
β (˚) | 115.303 (2) |
V (Å3) | 1915.8 (5) |
Z | 4 |
Radiation type | MoKα |
µ (mm−1) | 1.70 |
Crystal size (mm) | 0.55 × 0.51 × 0.45 |
Data collection | |
Diffractometer | Bruker AXS SMART APEX CCD diffractometer |
Absorption correction | Multi-scan Apex2 v2011.2-0 (Bruker, 2011) |
Tmin, Tmax | 0.541, 0.746 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 11188, 3100, 2920 |
Rint | 0.016 |
(sin θ/λ)max (Å−1) | 0.746 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.021, 0.056, 1.07 |
No. of reflections | 3100 |
No. of parameters | 107 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e∙Å−3) | 0.50, −0.58 |
x | y | z | Uiso*/Ueq | |
---|---|---|---|---|
C1 | 0.17271 (10) | 0.68038 (9) | 0.35411 (8) | 0.01752 (19) |
H1 | 0.1613 | 0.7278 | 0.2969 | 0.021* |
C2 | 0.10691 (9) | 0.69632 (9) | 0.40965 (8) | 0.01576 (18) |
H2 | 0.0492 | 0.7537 | 0.3901 | 0.019* |
C3 | 0.12487 (9) | 0.62693 (8) | 0.49683 (8) | 0.01409 (17) |
C4 | 0.21230 (10) | 0.54235 (9) | 0.52141 (9) | 0.01694 (19) |
H4 | 0.2281 | 0.4945 | 0.5793 | 0.020* |
C5 | 0.27329 (10) | 0.53025 (9) | 0.46146 (9) | 0.0194 (2) |
H5 | 0.3307 | 0.4729 | 0.4777 | 0.023* |
C6 | −0.03134 (10) | 0.72447 (10) | 0.52349 (9) | 0.0211 (2) |
H6A | 0.0041 | 0.7979 | 0.5284 | 0.032* |
H6B | −0.0701 | 0.7206 | 0.5710 | 0.032* |
H6C | −0.0903 | 0.7115 | 0.4513 | 0.032* |
C7 | 0.08652 (11) | 0.57280 (10) | 0.64620 (9) | 0.0206 (2) |
H7A | 0.0762 | 0.4944 | 0.6266 | 0.031* |
H7B | 0.0315 | 0.5931 | 0.6765 | 0.031* |
H7C | 0.1685 | 0.5858 | 0.6980 | 0.031* |
N1 | 0.25385 (8) | 0.59811 (8) | 0.37942 (7) | 0.01860 (18) |
H1A | 0.2945 | 0.5886 | 0.3421 | 0.022* |
N2 | 0.06171 (8) | 0.64013 (8) | 0.55294 (7) | 0.01696 (17) |
Cl1 | 0.34860 (2) | 0.68118 (2) | 0.207499 (19) | 0.01598 (6) |
Cl2 | 0.42347 (2) | 0.43620 (2) | 0.32353 (2) | 0.01864 (6) |
Cu1 | 0.5000 | 0.559866 (14) | 0.2500 | 0.01307 (5) |
bond angles of 141.19 (1)˚ for both Cl2-Cu1-
Examination of the crystal structure of the title salt (
Anions and cations are linked by a network of N-H・・・Cl and C-H・・・Cl hydrogen bonds into a three dimensional network. Among these hydrogen bonds, one is bifurcated N1-H1A・・・(Cl1, Cl2) (
The geometric features of the organic cations are given in
C1-N1 | 1.3517 (14) | C1-C2 | 1.3663 (15) |
---|---|---|---|
C2-C3 | 1.4244 (14) | C7-N2 | 1.4625 (14) |
C3-N2 | 1.3412 (13) | C3-C4 | 1.4233 (14) |
C4-C5 | 1.3632 (15) | Cl1-Cu1 | 2.2562 (4) |
C5-N1 | 1.3526 (15) | Cl2-Cu1 | 2.2491 (3) |
C6-N2 | 1.4631 (14) | Cu1-Cl2i | 2.2491 (3) |
C6-N2 | 1.4631 (14) | Cu1-Cl1i | 2.2562 (4) |
N1-C1-C2 | 120.99 (10) | C1-N1-C5 | 120.83 (10) |
C1-C2-C3 | 119.98 (9) | N1-C5-C4 | 121.42 (10) |
N2-C3-C4 | 121.39 (10) | C3-N2-C7 | 120.80 (9) |
N2-C3-C2 | 121.55 (9) | C3-N2-C6 | 120.47 (9) |
C4-C3-C2 | 117.06 (9) | C7-N2-C6 | 118.71 (9) |
C5-C4-C3 | 119.71 (10) | ||
Cl2i-Cu1-Cl2 | 96.668 (18) | Cl2i-Cu1-Cl1 | 141.190 (11) |
Cl2i-Cu1-Cl1i | 94.882 (13) | Cl2-Cu1-Cl1 | 94.879 (13) |
Cl2-Cu1-Cl1i | 141.189 (11) | Cl1i-Cu1-Cl1 | 98.908 (18) |
Symmetry code: (i) −x + 1, y, −z + 1/2.
D-H・・・A | D-H | H・・・A | D・・・A | D-H・・・A |
---|---|---|---|---|
N1-H1A・・・Cl1 | 0.88 | 2.53 | 3.2726 (10) | 143 |
N1-H1A・・・Cl2 | 0.88 | 2.53 | 3.2128 (12) | 135 |
C2-H2・・・Cl2ii | 0.95 | 2.63 | 3.5667 (13) | 167 |
C4-H4・・・Cl1iii | 0.95 | 2.78 | 3.6408 (13) | 152 |
C6-H6B・・・Cl1iv | 0.98 | 2.79 | 3.6832 (14) | 152 |
C7-H7C・・・Cl2iii | 0.98 | 2.90 | 3.8554 (15) | 163 |
C1-H1・・・Cl2v | 0.95 | 2.97 | 3.8347 (12) | 152 |
Symmetry codes: (ii) x − 1/2, y + 1/2, z; (iii) x, −y + 1, z + 1/2; (iv) x − 1/2, −y + 3/2, z + 1/2; (v) ?x + 1/2, y + 1/2, −z + 1/2.
amino group. Consequently, the basicity of the N2 nitrogen atom decreases, which is in favor of the protonation of the N1 nitrogen atom of the pyridinic ring. Moreover, the C-N-C angles of the pyridine are very sensitive to protonation [
As it can be seen clearly from
FTIR spectroscopy was used to identify the functional groups present in the crystal. The infrared absorption spectrum of (C7H11N2)2CuCl4 is shown in
Group1/Group2 | d(CgI…CgJ) | α(˚) | β(˚) | γ(˚) | Dist_perp |
---|---|---|---|---|---|
Cg1/Cg1i | 3.7622(5) | 0 | 25 | 25 | 3.4090 |
Symmetry codes: (i) 1/2 − x, 1/2 − y, −z. Cg1 is the centroid of N1-C5 ring. d(CgI…CgJ) is the distance between the centroids of rings. α is the dihedral angle between planes I and J. β is the angle between the vector CgI à CgJ and the normal to plane I. γ is the angle between the vector CgI àCgJ and the normal to plane J. Dist_perp is the interplanar distance between the parallel rings I and J.
n (C-C) modes. The band at 1070 cm−1 can be attributed to the d (C-C) mode. The remaining bands in the range 1000 to 500 cm−1 are assigned to γ (C-C), γ (C-H) and γ (C-N) out-of-plane bending modes.
DFT calculations showed that the inorganic entities lead to vibrations below 500 cm−1 which are not observed experimentally in our conditions. So we focused only on the vibrations of the organic cation. X-ray diffraction data give C-H or N-H distances which are too small compared to what is usually observed (typically below 0.1 nm) due to the fact that this method is not sensitive to the nuclei but to the electrons and so gives values corresponding to distances between the barycenters of electronic charges. As a consequence, the positions of protons were first optimized, the C and N atoms being located at the positions given by the X-ray study. The resulting C-H and N-H distances corresponded to what is usually obtained (typically 0.109 nm for C-H and 0.104 nm for N-H) and the frequencies calculation was made on this semi-optimized geometry. The resulting IR spectrum, calculated by the B3LYP/6-311++G** method, is plotted on
Bis(4-dimethylaminopyridinium) tetrachlorocuprate was synthesized and its structure is reported for the first time in the literature. In the atomic arrangement, the organic layers, built up by the 4-dimethylaminopyridinium cations, are arranged in sandwich between the
Crystallographic data for the structural analysis have been deposited with the Cambridge Crystallographic Data Centre, CCDC No 1047063. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK: fax: (+44) 01223-336-033; e-mail: deposit@ccdc.cam.ac.
We would like to acknowledge the support provided by the Secretary of State for Scientific Research and Technology of Tunisia. The X-ray diffractometer was funded by NSF Grant 0087210, Ohio Board of Regents Grant CAP-491, and by Youngstown State University of USA. A special thank you is needed for Dr. Matthias Zeller, who has helped in collecting and processing X-ray crystallography data.