Synthesis, Structure, and Spectroscopic Properties of Copper(II) and Nickel(II)Complexes Containing the 1,4,7-Triisopropyl-1,4,7-triazacyclononane Ligand

Wei Hana, Ling Lia, Zhan-Quan Liua, Shi-Ping Yan*,a,b, Dai-Zheng Liaoa, Zong-Hui Jianga, andPan-Wen Shena

a Tianjin / People’s Republic of China, Nankai University, Department of chemistryb Beijing / People’s Republic of China, Peking University, State Key Laboratory of Chemistry and Application of Rare Earth Materials

Received October 10th, 2003.

Abstract. Three new complexes [CuL(N3)2] (1), [CuL(SCN)2] (2),and [NiL(SCN)2] (3) (L � 1,4,7-triisopropyl-1,4,7-triazacyclo-nonane, [�NR�C2H4�NR�C2H4�NR�C2H4�], R � i-Pr) havebeen synthesized and structurally characterized. The three com-plexes all crystallize in the monoclinic space group P21/n, with theunit cell parameters a � 9.100(5), b � 19.492(11), c � 11.646(6) A,β � 94.526(9)° for 1, a � 10.148(3), b � 13.611(5), c � 15.777(6) A,β � 95.412(6)° for 2 and a � 9.270(7), b � 16.629(14), c �

14.886(12) A, β � 101.217(15)° for 3. The central copper(II) and

Synthese, Struktur und spektroskopische Eigenschaften der Kupfer(II)- und Nickel(II)-Komplexe mit dem 1,4,7-Triisopropyl-1,4,7-triazacyclononan Liganden

Inhaltsübersicht. Drei neue Komplexe [CuL(N3)2] (1), [CuL(SCN)2](2) und [NiL(SCN)2] (3) (L � 1,4,7-triisopropyl-1,4,7-triazacyclo-nonan, [�NR�C2H4�NR�C2H4�NR�C2H4�], R � i-Pr) wur-den synthetisiert und strukturell charakterisiert. Die drei Komplexekristallisieren in der monoklinen Raumgruppe P21/n, mit den Git-terparametern für 1: a � 9.100(5), b � 19.492(11), c � 11.646(6) A,β � 94.526(9)°, für 2: mit a � 10.148(3), b � 13.611(5), c �

Introduction

The past three decades have witnessed a rapid expansion inthe scope of the coordination chemistry of 1,4,7-triaza-cyclononane (TACN). Previous studies mostly carried outin the laboratory of Wieghardt, focused on the basic coordi-nation chemistry of TACN complexes and were reviewedby Wieghardt [1]. It has been recognized extensively thatTACN and its N-alkylated surrogates are excellent ligandsin supporting both mono- and bi-metallic complexes con-taining liable coordination sites. Hence, many of TACN andits N-substituted complexes are found to be both structuraland functional models of various metallo-enzymes [2�6].In addition, some TACN-based and its N-substituted com-plexes are found to be capable of promoting phosphate es-ter degradation and DNA cleavage [7�10]. During the

* Dr. Shi-Ping YanDepartment of ChemistryNankai UniversityTianjin 300071 / People’s Republic of ChinaTel.: �86-22-2350-9957; Fax: �86-22-2350-2779E-mail: yansp@nankai.edu.cn.

Z. Anorg. Allg. Chem. 2004, 630, 591�596 DOI: 10.1002/zaac.200300392 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 591

nickel(II) ions are coordinated to five nitrogen atoms, three ofwhich from the L and two from N3

� or SCN�, forming a slightlydistorted square pyramidal geometry. Moreover, elemental analysis,IR, UV-vis and ESR spectra of complexes 1-3 were also deter-mined.

Keywords: Copper; Nickel; Macrocyclic ligands; Crystal structure;Spectroscopic properties

15.777(6) A, β � 95.412(6)°, für 3 mit a � 9.270(7), b � 16.629(14),c � 14.886(12) A, β � 101.217(15)°. Die zentralen Kupfer(II)- undNickel(II)-Ionen werden von fünf Stickstoffatomen koordiniert,drei vom Liganden L und zwei vom N3

� oder SCN�, unter Bildungeiner leicht verzerrten quadratischen Pyramide. Die Komplexe wer-den durch Elementaranalysen, IR-, UV-vis- und ESR-Spektrencharakterisiert.

course of this work, we prepared three complexes contain-ing copper and nickel ions using 1,4,7-triisopropyl-1,4,7-triazacyclononane (L): [CuL(N3)2] (1), [CuL(SCN)2] (2),and [NiL(SCN)2] (3); their synthesis, structures, and spec-troscopic properties are reported here.

Results and Discussion

Structure description

The structures of complexes 1-3 are shown in Figures 1, 2and 3, respectively, and their selected bond lengths andangles are listed in Table 1. The central metal ions in thesecomplexes have a distorted square pyramidal coordinationwith the ligand L and two N3

� or SCN� ligands. For pur-pose of explicit discussion we chose copper atom in com-plex 1 as example to describe. In Figure 1, the basal planeposition is occupied by the N(2) and N(3) atoms of the Lligand, and the N(4) and N(7) atoms of two azide ions withthe average Cu�NL and Cu�Nazide bond lengths of2.154(5) A and 1.994 A, respectively. The apical position isoccupied by N(1) from L with a longer bond distance (2.260A) than those in basal plane. The Cu atom is displaced out

W. Han, L. Li, Z.-Q. Liu, S.-P. Yan, D.-Z. Liao, Z.-H. Jiang, P.-W. Shen

Fig. 1 Molecular structure of complex 1 showing the atom-number-ing scheme. Thermal ellipsoids represent 30 % probability and hy-drogen atoms are omitted for clarity.

of the basal plane by 0.158(7) A in the direction of the axialatom which is normally observed for the five-coordinatedsquare pyramidal geometry. The value of τ as defined byAddison et al. [11] is 0.25 [τ � (β � �) / 60, where� � N(7)�Cu(1)�N(2) � 158.80(19)°, β �N(4)�Cu(1)�N(3) � 173.96(17)°, τ � 0 and 1 for perfectsquare-pyramidal and trigonal-bipyramidal geometries,respectively] and indicates the distortion towards a square-pyramidal geometry. The τ values in the structurally charac-terized [CuL]� or [CuL]2� with different terminal orbridged ligands, are listed in Table 2. In complex 2, the aver-age Cu�NL and Cu�NSCN� bond lengths in the basalplane are 1.959(3) A and 2.086(8) A, respectively, and thebond of the axial position is also relatively long(2.254(3) A). The corresponding τ value is 0.27, which indi-cates a slightly stronger irregularity in the geometry thanthat found in complex 1. The difference in the values of τof 1 and 2 indicates that a more regular conformation instereochemistry is constituted when the auxiliary ligand waschanged from thiocyanate to azide. The average bondlengths of Ni�NL and Ni�NSCN� in complex 3 are2.148 A and 2.016(1) A. Unlike complexes 1 and 2, theNi�N bond in the axial position is short with a length of2.087(5) A. This unusual phenomenon may be explained bythe change of central ion from copper atom in 1 and 2 tonickel atom in 3. The value τ � 0.29 in complex 3 showsthat a much more irregular geometry was formed when thecentral ion was nickel, whereas the surrounding ligands re-mained unchanged.

IR Spectrum

All of the complexes have a similar IR spectra. The ν(C-H)stretching frequency of in L is indicated by a shoulder band

2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim zaac.wiley-vch.de Z. Anorg. Allg. Chem. 2004, 630, 591�596592

Fig. 2 Perspective view of complex 2 with the atom-numberingscheme. Thermal ellipsoids represent 30 % probability; hydrogenatoms are omitted for clarity.

Fig. 3 Perspective view of complex 3 with the atom-numberingscheme. Thermal ellipsoids represent 30 % probability; hydrogenatoms are omitted for clarity.

involving a split sharp peak at 2934 cm�1. A strong absorp-tion, νasym(N3), at 2043 cm�1 is observed for complex 1,however, the weak absorption band at about 1300 cm�1

[νsym(N3)] could not be identified unambiguously due tooverlapping bands in this region of the coordinated macro-cycle. In the complexes which contain N3

� ions, terminalcoordinated N3

� and µ-1,3-azide bridging ligands show

Copper(II) and Nickel(II) Complexes Containing the 1,4,7-Triisopropyl-1,4,7-triazacyclononane Ligand

Table 1 Selected bond lengths /A and angles /° for complexes 1, 2and 3

1Cu(1)-N(1) 2.260(4) N(4)-N(5) 1.172(6)Cu(1)-N(2) 2.178(4) N(5)-N(6) 1.144(7)Cu(1)-N(3) 2.131(4) N(7)-N(8) 1.198(6)Cu(1)-N(4) 1.999(4) N(8)-N(9) 1.162(6)N(2)-Cu(1)-N(1) 84.50(15) N(7)-Cu(1)-N(3) 92.7(2)N(3)-Cu(1)-N(1) 84.5(2) N(4)-Cu(1)-N(3) 174.0(2)N(7)-Cu(1)-N(1) 116.0(2) N(7)-Cu(1)-N(4) 92.9(2)N(4)-Cu(1)-N(1) 91.10(2) N(5)-N(4)-Cu(1) 124.5(4)N(3)-Cu(1)-N(2) 83.6(2) N(6)-N(5)-N(4) 175.5(8)N(4)-Cu(1)-N(2) 91.9(2) N(8)-N(7)-Cu(1) 126.9(4)N(7)-Cu(1)-N(2) 158.8(2) N(9)-N(8)-N(7) 175.3(6)

2Cu(1)-N(1) 2.254(3) N(4)-C(16) 1.150(4)Cu(1)-N(2) 2.087(3) C(16)-S(1) 1.616(4)Cu(1)-N(4) 1.966(3) N(5)-C(17) 1.161(4)Cu(1)-N(5) 1.952(3) C(17)-S(2) 1.608(4)N(5)-Cu(1)-N(1) 111.7(1) N(5)-Cu(1)-N(3) 161.6(1)N(4)-Cu(1)-N(1) 93.1(2) N(4)-Cu(1)-N(3) 94.3(1)N(3)-Cu(1)-N(1) 86.3(1) N(5)-Cu(1)-N(4) 88.8(1)N(2)-Cu(1)-N(1) 84.9(1) C(16)-N(4)-Cu(1) 155.9(3)N(5)-Cu(1)-N(2) 92.9(1) N(4)-C(16)-S(1) 178.8(4)N(4)-Cu(1)-N(2) 177.7(1) C(17)-N(5)-Cu(1) 161.8(3)N(3)-Cu(1)-N(2) 84.6(1) N(5)-C(17)-S(2) 178.9(4)

3Ni(1)-N(1) 2.087(5) N(4)-C(16) 1.154(8)Ni(1)-N(2) 2.140(5) C(16)-S(1) 1.649(8)Ni(1)-N(3) 2.155(5) N(5)-C(17) 1.176(7)Ni(1)-N(4) 2.026(6) C(17)-S(2) 1.631(8)Ni(1)-N(5) 2.004(6)N(2)-Ni(1)-N(1) 87.2(2) N(5)-Ni(1)-N(3) 92.5(2)N(3)-Ni(1)-N(1) 86.8(2) N(4)-Ni(1)-N(3) 176.7(2)N(5)-Ni(1)-N(1) 112.8(2) N(5)-Ni(1)-N(4) 89.1(2)N(4)-Ni(1)-N(1) 95.3(2) C(16)-N(4)-Ni(1) 169.5(6)N(3)-Ni(1)-N(2) 83.0(2) N(4)-C(16)-S(1) 179.7(7)N(5)-Ni(1)-N(2) 159.3(2) C(17)-N(5)-Ni(1) 175.0(6)N(4)-Ni(1)-N(2) 94.5(2) N(5)-C(17)-S(2) 179.0(6)

similar absorptions [15]. The band at 2043 cm�1 shows thatthe azide is a terminal ligand rather than µ-1,3 bridgingligands (νasym(N3) at 2100 cm�1). This result was consistentwith the crystal structure. In complexes 2 and 3, the pres-ence of NCS� stretching vibrations at 2054 and 2055 cm�1

suggest that this group is coordinated to the metal ions asa terminal ligand. The band at 2100 cm�1 falls in the regionexpected for an end-to-end bridging ligand and that at2050 cm�1 in the region expected for terminal NCS [16, 17].Additionally, the lack of any absorption in the region 670-

Table 2 Cu-N and Cu-O distance /A and τ values for [CuL]� and [CuL]2� complexes

Compound coord. sphere axial equatorial τ ref.

1 5N 2.260(4) 1.989(5), 1.999(4) 0.25 this work2.131(4), 2.178(4)

2 5N 2.254(3) 1.952(3), 1.966(3) 0.27 this work2.086(3), 2.087(3)

3 5N 2.087(5) 2.005(6), 2.026(6) 0.29 this work2.140(5), 2.155(5)

[CuL(O2CCH3)2] 3N, 2O 2.288(5) 1.936(5), 1.957(4) 0.27 [12]2.132(5), 2.088(5)

[CuL(H2O)(O3SCF3)]� 3N, 2O 2.180(5) 2.046(5), 2.070(5) 0.35 [13]2.014(5), 2.052(4)

[(CuIL)2(µ-NO2)]� 3N, 2O 2.13(1), 2.047(9) 0.08 [14]

Z. Anorg. Allg. Chem. 2004, 630, 591�596 zaac.wiley-vch.de 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 593

780 cm�1 strongly argues in favor of the absence of sulfur-bonded terminal NCS� groups. All of these results arequite consistent with the crystal structure.

Electronic Spectrum

The electronic spectra of complexes 1 and 2 are all verysimilar because ofthe same central copper ions (Fig. 4,Table 4). The spectra show very strong absorption bands at315 nm for 1 and 294 nm for 2, which can be attributed toπ-π* charger transfer of the ligand itself. The shoulder bandat 405 nm of complex 1 can be ascribed as CuII � L MLCTcharge-transfer transition. In addition, a weak, broad ab-sorption centered at 706 nm of 1 and 692 nm of 2 can bedesignated as the typical d-d electronic-transfer absorptionin CuII (3d9) ground state in C4ν. In complex 3, the spectracomprising of five bands at 416, 696, 762, 1002 and1452 nm indicate a typical absorption for a square pyrami-dal, high spin NiII complexe [18]. The five absorption bandscan be ascribed to the d-d electron-transfer bands in NiII

(3d8) ground state in C4ν. The corresponding transitionsare: 3B1 (F) �3A2 (F), 3B1 (F) �3E (F), 3B1 (F) �3B2 (F),3B1 (F) �3A2 (F) and 3B1 (F) �3E (F), respectively. Theabsorption band at about 352 nm has not been observedbecause of the strong absorption of the MLCT and thecharger-transition of the ligand itself in this region.

ESR

The X-band ESR spectra of powdered complexes 1 and 2at room temperature and at 110 K have been measured.The ESR spectrum of 1 at room temperature displays anasymmetric absorption (Fig. 5), while it shows three differ-ent g tensors with a hyperfine structure in the gy signal at110 K. The computer simulation gave the ESR parametersgx � 2.06, gy � 2.14, gz � 2.20. The g values of 1 and 2and related [CuL]� or [CuL]2� complexes are listed in Table4. According to Reinen [19], the ground-state wave functionof five-coordination copper(II) complexes with intermedi-ate geometry TBP (trigonal bipyramid) and SP (squarepyramid) is expressed by

ϕg � (1 � c2)1/2 [dz2 � cdx2�y2]

W. Han, L. Li, Z.-Q. Liu, S.-P. Yan, D.-Z. Liao, Z.-H. Jiang, P.-W. Shen

Table 3 Data collection and processing parameters for complexes 1, 2 and 3

1 2 3

Formula C15H33CuN9 C17H33CuN5S2 C17H33N5NiS2

Formula weight 403.04 435.14 430.31Temperature/K 273(2) 293(2) 293(2)Wavelength/A 0.71073 0.71073 0.71073Crystal system monoclinic monoclinic monoclinicSpace group P21/n P21/n P21/nUnit cell dimensions a � 9.100(5) A a � 10.148(3) A a � 9.270(7) A

b � 19.492(11) A b � 13.611(5) A b � 16.629(14) Ac � 11.646(6) A c � 15.777(6) A c � 14.886(12) Aβ � 94.562(9)° β � 95.412(6)° β � 101.217(15)°

V/A3 2059(2) 2169.5(13) 2251(3)Z 4 4 4Dcalcud/Mgm

�3 1.300 1.332 1.270µ/mm�1 1.078 1.209 1.057F(000) 860 924 920Crystal size/mm 0.30�0.25�0.20 0.32�0.28�0.24 0.15�0.15�0.08θ range for data collection/° 2.04�25.03 2.29�26.44 1.86�25.03Limiting indices �9 � h � 10, �12<�h<�11 �11<�h<�10

�18 � k � 23 �17<�k<�14 �10<�k<�19�13 � l � 12 �19<�l<�14 �17<�l<�17

Reflections collected 7009 10064 8855Unique reflections 3474 4349 3881Absorption correction SADABS SADABS SADABSMax. and min. transmission 0.8133 and 0.7381 1.0000 and 0.8103 0.9202 and 0.8575Refinement method Full-matrix least squares on F2 Full-matrix least squares on F2 Full-matrix least squares on F2

Data / restraints / parameters 3474/0/232 4349/0/227 3881/0/232Goodness-of-fit on F2 1.009 0.965 0.941Final R indices [I > 2 σ(I)] R1 � 0.0477, R1 � 0.0497 R1 � 0.0704

wR2 � 0.0990 wR2 � 0.0820 wR2 � 0.1388R indices (all data) R1 � 0.1131, R1 � 0.1124 R1 � 0.1675

wR2 � 0.1477 wR2 � 0.0979 wR2 � 0.1732Largest peak and hole/e A�3 0.413 and �0.429 0.334 and �0.310 0.928 and �0.633

Fig. 4 UV-vis spectra of DMSO solutions of [CuL(N3)2] (�-) and[CuL(SCN)2] (�).

in which the mixing cofficient is c � 0 for the trigonal bi-pyramid (dz2 ground state) and c � 1/31/2 for the squarepyramid with a dx2�y2 ground state. Based on above func-tion, we used the three simulated g values and the electronicabsorption spectrum data (706 nm in 1), getting the valueof c is close to 1/31/2 (0.53) for 1. This c value indicates thatthe geometry of complex 1 have little degree of distortionfrom SP, which is in agreement with the result of the crystalstructure. This method has also been carried out on com-plex 2 and the same result was obtained and the corre-sponding c value is 0.50.

2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim zaac.wiley-vch.de Z. Anorg. Allg. Chem. 2004, 630, 591�596594

Table 4 Summary of selected spectroscopic data for 1 and 2 andrelated complexes

Complex ESR UV-vis Ref.

1 gx � 2.06, gy � 2.14, 315, 405, this workgz � 2.20 706c)

2 g� � 2.02, g� � 2.25 294, 692c) this workA� � 160a)

[CuL(O2CCH3)2] g� � 2.06, g� � 2.30 298, 684d) [12]A� � 154�10�4b)

[CuL(O3SCF3)2] g� � 2.09, g� � 2.28 300, 718d) [14]A� � 160�10�4b)

[(CuIL)2(µ-NO2)]2� g� � 2.07, g� � 2.24 314, 356, [13]A� � 136�10�4b) 444, 668d)

a) A� value quote in G; measured at 110 K in DMSO. b) A� value quote incm�1; measured at 77 K as 1:1CH2Cl2/toluene glasses. c) λmax, nm; measuredat room temperature as solutions in DMSO. d) λmax, nm; measured at roomtemperature as solutions in CH2Cl2.

Experimental Section

General

All reagents and chemicals were of commercially available reagentquality and were used without further purification. 1,4,7-Triaza-cyclononane (TACN) was prepared according to the previous pro-cedure [20, 21] and 1,4,7-triisopropyl-1,4,7-triazacyclononane wassynthesized as previously described [22]. Elemental analyses (C, H,N) were performed on a Perkin-Elmer 240 analyser. IR spectrawere recorded on a Nicolet 5DX FTIR spectrometer as KBr pellets,electronic spectra on a Shimadzu UV-2101PC UV-vis scanningspectrophotometer in DMSO, X-band ESR spectra on a Bruker

Copper(II) and Nickel(II) Complexes Containing the 1,4,7-Triisopropyl-1,4,7-triazacyclononane Ligand

Fig. 5 X-band ESR spectra of complex 1 in powder at room tem-perature (top), and powder at 110 K (a) and simulation spectrum(b) (bottom).

ER-200-DSR10 ESR spectrometer, and single-crystal analyses ona Bruker Smart 1000 diffractometer.

[CuL(N3)2] (1): A solution of Cu(ClO4)2·6H2O (0.19 g, 0.5 mmol)in methanol (5 mL) was added to the i-Pr3TACN (0.13 g,0.5 mmol) in methanol (15 mL), affording a clear, deep blue solu-tion, the reaction mixture was stirred for 30 min at room tempera-ture, then a solution of NaN3 (0.07 g, 1 mmol) in water (5 mL) wasthen slowly added drowise; the deep blue mixture was stirred foranother 2 h, then filtered to get rid of any insoluble particles. Thedeep blue crystals of 1 suitable for X-ray crystallographic analysiswere obtained by slow evaporation of the filtrate. C15H33CuN9

(403.04); C 44.73 (calc. 44.66); H 8.19 (8.43); N 31.39 (31.26) %.

[CuL(SCN)2] (2): Complex 2 was synthesized with the similarmethod to 1. A suspension of Cu(ClO4)2·6H2O (0.19 g, 0.5 mmol)and the macrocycle (0.13 g, 0.5 mmol) in methanol (20 mL) give ablue solution, NH4SCN (0.08 g, 1 mmol) in water (5 mL) was ad-ded slowly to the aforementioned solution and the resulting deepblue solution was stirred for 2 h, then filtered to get rid of any solid

Z. Anorg. Allg. Chem. 2004, 630, 591�596 zaac.wiley-vch.de 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 595

particals. A few week later, dark blue crystals suitable for X-raycrystallographic analysis of 2 were obtained. C17H33CuN5S2

(435.14); C 46.91 (46.88); H 7.59 (7.83); N 16.17 (16.09) %.

[NiL(SCN)2] (3): Complex 3 was prepared in an analogous mannerto that of 2 but using Ni(ClO4)2·6H2O (0.18 g, 0.5 mmol). The cleargreen solution left at room temperature to yielded suitable for X-ray quality pale blue crystals. C17H33N5NiS2 (430.31); C 47.68(47.41); H 7.67 (7.95); N 16.39 (16.27) %.

X-ray structure analysis

Data collections were performed on a Bruker Smart diffractometerequipped with CCD area detector (MoKα radiation, λ �

0.71073 A) by ϕ and ω; scan technique at 293(2) K. The structurewas solved by direct methods (SHELX-97)[23] and refined by full-matrix least-squares methods with anisotropic thermal parametersfor non-hydrogen atom on F 2. The hydrogen atoms were addedtheoretically, and riding on the concerned atoms and refined withfixed thermal factors. Further details about crystal data and struc-ture refinement are summarized in Table 3.

Crystallographic data for the structures reported in this paper havebeen deposited with the Cambridge Crystallographic Data Centre,CCDC No. 1: 219831; 2: 219832 and 3: 219833. Copies of the datacan be obtained free of charge on application to CCDC, 12 UnionRoad, Cambridge CB2 1EZ, UK (fax: (internat.) �44-1223/336-033; e-mail: deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.a-c.uk).

Acknowledgement. This work was supported by the National Natu-ral Science Foundation of China (No. 20171026) and Tianjin Natu-ral Science Foundation (No. 013605811).

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