Syntheses and Crystal Structures of Two Copper Complexes Based on Quinolyl and Pyridyl Substituted Triaryltriazoles

FENG ZheGAO Jian-FeiLI GangZHU Dun-Ru＊，，2

(1College of Chemical Engineering,State Key Laboratory of Materials-Oriented Chemical Engineering,Nanjing Tech University,Nanjing 211816,China)

(2State Key Laboratory of Coordination Chemistry,Nanjing University,Nanjing 210023,China)

Abstract:Two new copper（Ⅱ） complexes，trans-[Cu(L1)2(NO3)(H2O)]NO3·H2O(1)and trans-[Cu(L2)2(NO3)(H2O)]NO3·H2O(2)(L1=3-(2-pyridyl)-4-(p-methylphenyl)-5-(2-quinolyl)-1，2，4-triazole，L2=3-(2-pyridyl)-4-(p-fluorophenyl)-5-(2-quinolyl)-1，2，4-triazole)，were synthesized and characterized by FT-IR，elemental analyses and single-crystal X-ray crystallography.Both 1 and 2 crystallize in triclinic system with space group P.X-ray crystallography analysis reveals that the copper ion in 1 and 2 lies in a distorted octahedral environment[CuN4O2]with one nitrate and one water molecule，respectively in the trans-position.The L1or L2ligand coordinates with Cu（Ⅱ） via one pyridine N atom and one triazole N atom，while the quinolyl group does not take part in coordination.In 1 and 2 there are some intermolecular O-H…O，C-H…O and C-H…N hydrogen bonds and C-H…π interactions，connecting the mononuclear complexes to form a 3D framework.CCDC:1975981，1;1975982，2.

Keywords:synthesis;Cu（Ⅱ）complex;crystal structure;triaryltriazole

3，4，5-Triarylsubstituted 1，2，4-triazole is a kind of very useful ligand in coordination chemistry due to its rich and versatile coordination modes[1-2].Specially，some iron（Ⅱ）complexes based on the triaryltriazole can show interesting spin-crossover properties[3]，which makes them be a type of potential molecular-based materials used as memory devices，displays and switching[4-5].In order to explore novel triaryltriazole-based iron（Ⅱ） spin-crossover complexes，a series of 4-arylsubstituted 3，5-di(2-pyridyl)-1，2，4-triazoles[6-12]and asymmetrically 3，4，5-triarylsubstituted 1，2，4-triazoles[13-25]have been designed and synthesized successfully.Among them，the pyridyl，phenyl，pyrrolyl，imidazolyl and benzimidazolyl groups are the known aromatic rings attached on the 3，4，5-triarylsubstituted 1，2，4-triazoles.However，the quinolyl group，an important alkaloid with stronger conjugated system，is less observed to connect on the 1，2，4-triazoles.Up to now only two quinolyl substituted 1，2，4-triazoles have been reported by us[26-27].As a continuation of our investigation of the quinolyl substituted 1，2，4-triazoles，we designed and synthesized two new triaryltriazoles:3-(2-pyridyl)-4-(p-methylphenyl)-5-(2-quinolyl)-1，2，4-triazole(L1)and 3-(2-pyridyl)-4-(p-fluorophenyl)-5-(2-quinolyl)-1，2，4-triazole (L2)as shown in Scheme 1.Herein we present the syntheses，crystal structures and spectral characterization of two copper（Ⅱ）complexes based on these ligands:trans-[Cu(L1)2(NO3)(H2O)]NO3·H2O(1)and trans-[Cu(L2)2(NO3)(H2O)]NO3·H2O(2).

Scheme 1 Structures of the ligands L1and L2

1 Experimental

1.1 Materials and measurements

All chemicals used were of analytical grade.Solvents were purified by conventional methods.The ligands L1and L2were synthesized via a similar literature method[23].Elemental analyses (C，H，N)were carried out with a Thermo Finnigan Flash 1112A elemental analyzer.IR spectra were recorded on a Nicolet Avatar 380 FT-IR instrument with KBr pellets in a range of 4 000～400 cm-1.

1.2 Syntheses of complexes 1 and 2

A solution of Cu(NO3)2·3H2O(0.05 mmol)in MeOH(3 mL)was added to a solution of L1(0.1 mmol)in anhydrous MeOH (3 mL).The mixture was stirred for 4 h at room temperature.A resulting green product was filtered and washed with H2O，then dried under vacuum to give 0.042 mmol(84%)of complex 1.The green single crystals of 1 suitable for X-ray diffraction were obtained by slow evaporation from the MeOH/MeCN (1∶1，V/V)solution of the complex.Elemental analyses Calcd.for C46H38CuN12O8(%):C，58.13;H，4.03;N，17.69.Found(%):C，57.81;H，4.25;N，17.46.IR(KBr，cm-1):3 343(w)，3 049(w)，3 011(w)，2 918(w)，1 597(m)，1 498(s)，1 387(vs)，1 289(m)，1 086(w)，828(m)，761(m).

The prepared procedure for 2 was the same as that for 1 except using L2(0.1 mmol)to replace L1.Yield:86.2%.Elemental analyses Calcd.for C44H32Cu F2N12O8(%):C，55.14;H，3.37;N，17.54.Found(%):C，55.31;H，3.26;N，17.69.IR (KBr，cm-1):3 379(w)，3 075(w)，1 596(m)，1 508(vs)，1 384(s)，1 236(m)，1 155(w)，839(m)，759(m).

1.3 Crystal structure determination

The well-shaped single crystals of 1 and 2 were selected for X-ray diffraction study.The unit cell parameters and intensity data were collected at 296(2)K on a Bruker SMART APEXⅡCCD diffractometer using a graphite-monochromated Mo Kα (λ=0.071 073 nm)radiation.The structures were solved by direct methods and refined on F2by full-matrix least squares procedures using SHELXTL software[28].All nonhydrogen atoms were refined anisotropically.All hydrogen atoms were fixed in calculated positions and refined isotropically.Two NO3-anions，O1W and O2W were found to be highly disordered with an occupancy factor of 0.5.Due to the disorder，the hydrogen atoms on the water were not calculated.The crystallographic data of 1 and 2 are listed in Table 1，and the selected bond lengths and angles are provided in Table 2.

CCDC:1975981，1;1975982，2.

Table 1 Crystal data and structure refinement for 1 and 2

Table 2 Selected bond distances(nm)and bond angles(°)for 1 and 2

2 Results and discussion

2.1 Synthesis

Asymmetrically quinolyl substituted 3，4，5-triaryl-1，2，4-triazoles(L1and L2)react with Cu(NO3)2·3H2O in molar ratio of 2∶1 to form two monomeric complexes，trans-[Cu(L1)2(NO3)(H2O)]NO3·H2O(1)and trans-[Cu(L2)2(NO3)(H2O)]NO3·H2O(2)，which are stable in air.The yields for 1 and 2 are 84%and 86.2%，respectively.The elemental analyses were satisfactory and indicate that both 1 and 2 contain one Cu（Ⅱ），two triazole ligands，two NO3-and two water molecules.

2.2 Crystal structures of 1 and 2

The crystal structures of 1 and 2 are presented in Fig.1 together with the atomic labeling system.Complexes 1 and 2 all crystallize in the triclinic space group Pand there is an inversion center at the Cu（Ⅱ）ion.Because 1 and 2 are isostructural complexes，herein，only the structure of 1 is discussed in detail.The asymmetric unit of 1 consists of half Cu（Ⅱ） cation，one L1ligand，one coordinated NO3-and H2O molecule(their occupancy factors are 0.5)，one NO3-counter ion and one lattice H2O molecule(their occupancy factors are also 0.5)，which is agreement with the elemental analysis result.The Cu（Ⅱ）ion of 1 is coordinated by four nitrogen atoms from two L1ligands in the equatorial plane and two oxygen atoms from NO3-and H2O in the axial positions to form a distorted octahedral[CuN4O2]geometry.Each L1ligand coordinates to Cu（Ⅱ）ion via N1 atom of the pyridyl and N2 atom of the triazole，similar to the coordination modes in some related Cu（Ⅱ） complexes[13，15，17，29-30].The quinolyl group of L1ligand is uncoordinated，which is different from the Fe（Ⅱ）complex with quinolyl substituted triaryltriazole: cis-[FeL2(NCS)2](L=3-(p-methylphenyl)-4-phenyl-5-(2-quinolyl)-1，2，4-triazole)[27].The distance of Cu1-O1(0.269 7 nm)is longer than the Cu1-O1W one(0.239 7 nm).The Cu-N bond lengths are within the normal ranges observed for the octahedral Cu（Ⅱ）complexes[13，15，17，29-30].However，the Cu-N bond to the triazole nitrogen is 0.006 3 nm shorter than that to the pyridyl nitrogen.The same feature has been observed in the similar Cu（Ⅱ） complexes[13，15，17].The ligand L1in 1 is non-planar.The triazole makes dihedral angles of 4.8(3)°，10.1(3)°and 83.3(3)°with the quinolyl ring，the pyridyl ring and p-methylphenyl ring，respectively.The corresponding angles in L2of 2 are 8.7(3)°，9.0(3)°and 86.8(3)°，respectively.

There are many intermolecular hydrogen bonds interactions in 1 (Fig.2，Table 3)，associated with the closer crystal packing.These hydrogen bond interactions include:(1)between water molecules and NO3-anion (O1W…O4 and O2Wi…O1i);(2)between pyridyl group and triazole ring (C1-H1A…N3i);(3)between pyridyl and NO3-anion (C2-H2A…O3iiand C3-H3A…O4ii);(4)between quinolyl group and the coordinated NO3-(C10-H10A…O2iiiand C12-H12A…O1iii); (5)between p-methylphenyl ring and the uncoordinated NO3-(C22-H22A…O4).In addition，there are an intramolecular edge-to-face C-H…π interaction involving C4-H4A and p-methylphenyl ring(H4A…π 0.294 nm and∠C4-H4A…π=145°)and an intermolecular edge-to-face C-H…π interaction involving C19-H19A and the phenyl ring of quinolyl group (H19A…π 0.326 nm and∠C19-H19A…π=141°)(Table 3，F(xiàn)ig.2).Notably，in 1 an offset face-to-face π-π stacking interaction exists between the phenyl ring of quinolyl group and pyridyl ring(dihedral angle:12.2(3)°)with a centroid-centroid distance of 0.382 nm(Fig.2，Table 4)，while the corresponding stacking is not found in 2.These extensive hydrogen bonds and C-H…π interactions assemble the mononuclear units，NO3-anions and lattice water molecule into a 3D framework of the complexes(Fig.3).

Fig.1 Projection of structures of 1 and 2 with 30%thermal ellipsoids probability

Fig.2 Hydrogen-bonding，C-H…π and π…π interactions in 1 and 2

Table 3 Hydrogen-bond geometry and C-H…π interactions in 1 and 2

Table 4 π…π interaction in 1

Fig.3 Three-dimensional frameworks of 1 and 2

2.3 IR spectra

In the IR spectra of complexes 1 and 2，a weak broad peak at 3 343 cm-1(1)or 3 379 cm-1(2)can be attributed to the O-H stretching vibrations of water molecules.A medium band at 1 597 cm-1(1)or 1 596 cm-1(2)can be assigned to the coordinated pyridyl ring vibration[14].A strong band at 1 384 cm-1is assigned to characteristic N=O stretching vibrations of NO3-in 1 and 2[31].In addition，the stretching vibration of F-C(Ph)in 2 can be observed at 1 236 cm-1[32].These features are in consistent with the results of the X-ray analysis.

3 Conclusions

Two new Cu（Ⅱ）complexes based on the quinolyl and pyridyl substituted triaryltriazole have been synthesized and characterized by IR and X-ray crystallography.Structural analyses indicate that two complexes have a similar distorted octahedral[CuN4O2]core with one nitrate and one water molecule，respectively in the trans-position.