Polyhedron 25 (2006) 3285–3288 www.elsevier.com/locate/poly

Nonlinear optical properties and crystal structure determination of a pentanuclear copper(I) cluster (NEt4)2[MoS4(CuBp)4] (Bp = H2B(pyrazolyl)2) Moayad Hossaini Sadr a,b,*, Jaber Jahanbin Sardroodi a,b, Davood Zare Neil R. Brooks c, William Clegg c, Yinglin Song d

a,b

,

a

Department of Chemistry, Azarbaijan University of Tarbiat Moallem, Tabriz, Iran b Research Institute for Fundamental Sciences, Tabriz, Iran c Department of Chemistry, University of Newcastle, Newcastle upon Tyne, NE1 7RU, UK d Department of Applied Physics, Harbin Institute of Technology, Harbin 150001, PR China Received 20 March 2006; accepted 4 June 2006 Available online 10 June 2006

Abstract The pentanuclear cluster complex (NEt4)2[MoS4(CuBp)4] has been prepared in acetone as a new candidate for nonlinear optical activity. The NLO properties of the cluster were studied, giving n2 = 4.2 · 1011 esu and b = 2.2 · 1010 m W1. The structure of the complex has been determined by single-crystal X-ray diffraction. The coordination environment around each copper atom is distorted tetrahedral with two N donors of the bidentate bis(pyrazolyl)borate ligands and two S donors of the MoS4 group, offering a structural model for some copper proteins. The Mo atom retains the tetrahedral geometry of the free [MoS4]2 anion and lies on a position with crystallographic S4 symmetry.  2006 Elsevier Ltd. All rights reserved. Keywords: Thiometallate; Polypyrazolylborate; Copper complexes; Nonlinear optical properties; Model compounds

1. Introduction The synthesis and characterization of clusters containing tetrathiometallate anions of tungsten and molybdenum, [MS4]2 (M = Mo, W), has been a fertile area of research with respect to their physico-chemical, bio-inorganic, and structurally oriented coordination chemistry [1–8]. In particular, the chemistry of these multidentate chelating ligands with copper(I), because of their high tendency to form Cu–S bonds, has attracted much attention [8–13]. Tetrathiomolybdates which are formed in the complex *

Corresponding author. Address: Department of Chemistry, Azarbaijan University of Tarbiat Moallem, Tabriz, Iran. Tel.: +98 412 4524983; fax: +98 412 452 4991. E-mail addresses: [email protected], [email protected] (M. Hossaini Sadr). 0277-5387/$ - see front matter  2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2006.06.001

stomach of ruminants from molybdate and electron-rich sulfide can act as efficient chelating ligands for positively charged, albeit p electron-rich (‘soft’), metal ions such as Cu+ and cause copper deficiency in them [14]. Recently, some medicinal applications of tetrathiomolybdate have been reported [15,16]. In addition to industrial applications [17], the nonlinear optical (NLO) properties of heterothiometallic clusters are a further incentive for researchers [18]. Recently we have published some papers on copper complexes which were the first examples containing both N-donor bispyrazolylborate and S-donor tetrathiometallate ligands [19–21] and offering potential models of copper proteins [22]. Poly(pyrazolyl)borates, [HnB(pz)4n], are anionic nitrogen-donor ligands, which form a wide variety of stable inorganic and organometallic compounds with structural and functional importance [23–27]. In addition, the pyrazole rings are similar to the imidazole function of

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the amino acid histidine of living systems. Therefore, these scorpionate ligands were selected as a second group to construct an N2S2 or NS2 coordination around copper atoms. As has been pointed in our previous publications, this type of cluster can exhibit nonlinear optical activity. Here we report the NLO properties and crystal structure of (NEt4)2[MoS4(CuBp)4]; the synthesis of the complex has been reported previously [21]. 2. X-ray crystallography experimental Suitable crystals for X-ray crystallography were obtained by diffusing Et2O into a saturated acetone solution of the title complex and leaving it for 3 days in a refrigerator. Diffraction studies of the title complex were performed on a Nonius KappaCCD diffractometer. ˚ ) was employed for Mo Ka radiation (k = 0.71073 A data collection at 150 K. Crystal data: (C8H20N+)2[C28H32Cu4MoN16S4]2, M = 1331.5, tetragonal, space ˚ , c = 32.490(7) A ˚, V= group I41/a, a = 13.341(2) A 3 1 ˚ 5782.6(17) A , Z = 4, l = 1.85 mm , crystal size 0.24 · 0.20 · 0.18 mm3; 51 790 reflections measured (2h < 27.5), 3311 unique (Rint = 0.0521); R [F2 > 2r(F2)] = 0.0277, Rw (all F2 values) = 0.0649, goodness of fit 1.067, final differ˚ 3. Absorption ence map extremes +0.34 and 0.62 e A corrections were semi-empirical from symmetry-equivalent and repeated reflections. The structure was solved by direct methods and refined by full-matrix least-squares on all unique F2. Non-hydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atoms were included in calculated positions and refined with isotropic displacement parameters riding on those of the parent atoms. Programs were standard Bruker AXS control and integration software, and SHELXTL [28]. 3. Description of crystal structure of (NEt4)2[MoS4(CuBp)4] (1) The Mo atom lies on a special position of S4 symmetry, and the cation lies on a C2 axis. The anion is constructed of one MoS4 and four symmetry-equivalent CuBp fragments linked through the bridging sulfur atoms, completely comparable to the analogous and isostructural tungsten complex [21] (unlike the tungsten complex, no twinning was detected in the molybdenum complex 1). There is no significant interaction between the dianion [MS4(CuBp)4]2 and the two Et4N+ counter-cations other than normal coulombic and van der Waals forces. A projection of the dianion of complex 1, with the atomic labelling scheme, is shown in Fig. 1 and selected bonding parameters are presented in Table 1. As in the precursor compounds [MS4(CuX)4]2 (M = Mo, W; X = Cl, Br) [29,30], the MoS4 core has retained its tetrahedral symmetry. Apparently, the symmetrical coordination of four CuL groups does not lower the symmetry of the MoS4 core significantly and the two unique S–Mo–S angles are very similar [108.65(2) and 111.13(3)]. All of the

Fig. 1. Structure of the [MoS4(CuBp)4]2 anion, showing the numbering scheme for the asymmetric unit. The view is inclined to the S4 axis.

Table 1 ˚ ) and bond angles () for (NEt4)2[MoS4(CuBp)4] Selected bond lengths (A Mo–S Cu–S(c) Cu–N(1) S–Mo–S(a) S–Cu–S(c) S–Cu–N(3) S(c)–Cu–N(3) Mo–S–Cu Cu–S–Cu(a)

2.2472(6) 2.2824(7) 2.110(2) 108.65(2) 105.31(3) 122.09(6) 119.11(6) 72.04(2) 111.97(3)

Cu–S Mo  Cu Cu(1)–N(3) S–Mo–S(b) S–Cu–N(1) S(c)–Cu–N(1) N(1)–Cu–N(3) Mo–S–Cu(a)

2.3097(7) 2.6801(5) 2.020(2) 111.13(3) 105.27(6) 111.13(6) 92.02(8) 72.55(2)

Symmetry operations for equivalent atoms: (a) y + 5/4, x + 1/4, z + 1/4; (b) x + 1, y + 3/2, z; (c) y  1/4, x + 5/4, z + 1/4.

˚ , slightly longer than those Mo–S distances are 2.2472(6) A of the similar bis-coordinated (NEt4)2[MoS4(CuBp 0 )2] ˚ ) [Bp 0 = H2B(PzMe2)2] [20] and rather longer (2.2103 A ˚ in the than in the uncomplexed [MoS4]2 anion (2.178 A ammonium salt) [31]. This elongation of Mo–S and reduction of its double bond character as a result of coordination is in agreement with the decrease of the m(Mo–S) stretching frequency in the IR spectrum. The very acute angles at the sulfur atoms bridging Cu and Mo [72.04(2) and 72.55(2)], together with the short Mo  Cu ˚ ) are suggestive of direct molybdenum– distances (2.680 A copper bonding interactions within the Cu(Sb)2Mo rings [Cu(I) (d10)–Mo(VI) (d0) charge delocalization]. Although no definitive statement can be made about the existence of a metal–metal bond, the observed distances are consistent with a strong attractive interaction between Cu and Mo

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atoms, as expected when placing two metals with greatly different formal oxidation states in close proximity, as they are in this pentanuclear cluster. The coordination environment of all of the copper atoms is highly distorted tetrahedral, with angles ranging from 92.02(8) (the bite angle of the chelating Bp ligand) to 122.09(6), and each Cu atom is coordinated by two sulfur atoms from MoS4 and two nitrogen atoms of a Bp ligand. The bond distances in the CuS2N2 coordination ˚ for Cu–S, and 2.020(2) and are 2.3097(7) and 2.2824(7) A ˚ 2.110(2) A for Cu–N. These values are in agreement with reported ones for previous compounds of this type [21,32] ˚ for Cu–S and or for similar compounds {e.g. 2.290(5) A ˚ 2.02(1) A for Cu–N in [WS4Cu3Cl(bpy)2] [33]}. In addition to the similarity between pyrazole (as N-donor in 1 and 2) and imidazole in histidine, the arrangement and coordination environment of the Cu atoms in 1 are comparable to those found in active sites of some copper proteins such as poplar plastocyanin, cuperedoxin, cytochrome c oxides, etc. [22,34,35], indicating that the synthesized complex 1 can serve as a model for some copper proteins. 4. Nonlinear optical properties Early investigations of planar-skeleton clusters revealed that the optical nonlinearity performance can be definitively attributed to the reverse saturable absorption under nanosecond pulsed radiation [36,37]. The Z-scan technique was applied to investigate the nonlinear optical refraction of (NEt4)2[MoS4(CuBp)4]. The output laser characteristics were as follows: pulse duration 8 ns; wavelength 532 nm; E = 0.1 mJ; 2 Hz repetition rate. The Z-scan scheme of complex 1 was calibrated using carbon disulfide (CS2), which is often used as a standard reference nonlinear material. The nonlinear refractive index of CS2 was measured as 2.5 · 1010 esu (13.9 · 1013 cm2 W1) at 532 nm, which is in good agreement with previously reported data measured in the nanosecond range [18,38]. In Fig. 2, the normalized transmittance dependence of the sample of 1 is presented for the closed-aperture Z-scan scheme; it shows that the cluster possesses strong reverse saturable absorption, and it could be considered as a promising candidate for optical limiting. The closed-aperture scheme allowed us to determine the sign and magnitude of n2 and Re X(3). The normalized transmittance has a pair of sharp peaks and a valley. The peak-valley configuration is characteristic of self-defocusing and indicates that the sample possesses negative nonlinear refraction. Both the width and amplitude of the valley are smaller than those of the peak. The asymmetry of the peak and valley is caused by the strong reverse saturable absorption. From the measured value of the difference of normalized transmittance at the peak and valley positions, DT = 0.18, the nonlinear optical refractive index n2 and Re X(3) were calculated to be 4.2 · 1011 esu and 1.069 · 1012 esu, respectively. The two-photon absorption coefficient b is 2.2 · 1010 m W1. These results are

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Fig. 2. The normalized transmittance dependence of (NEt4)2[MoS4 (CuBp)4] in the case of the closed-aperture scheme.

comparable with those for ZnO and suitable for optical limiting applications. Acknowledgements We thank the Research Institute for Fundamental Sciences (Tabriz, Iran) for financial support, EPSRC (UK) for equipment funding, and the Harbin Institute of Technology (China) for NLO measurements. Appendix A. Supplementary material Crystallographic data, excluding structure factors, have been deposited at the Cambridge Crystallographic Data Centre, CCDC No. 600512. Copies of this information may be obtained free of charge from the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: +44 1223 336 033; e-mail: [email protected] or www: http:// www.ccdc.cam.ac.uk). Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.poly.2006.06.001. References [1] (a) A. Mu¨ller, E. Diemann, R. Jostes, H. Bo¨gge, Angew. Chem., Int. Ed. Engl. 20 (1981) 934; (b) E. Diemann, A. Mu¨ller, Coord. Chem. Rev. 10 (1973) 79. [2] (a) R.H. Holm, Chem. Soc. Rev. 10 (1981) 455, and references therein; (b) J. Sola, Y. Do, J.M. Berg, R.H. Holm, J. Am. Chem. Soc. 105 (1983) 105; (c) Y. Do, E.D. Simhon, R.H. Holm, Inorg. Chem. 24 (1985) 4635. [3] (a) D. Coucouvanis, Acc. Chem. Res. 14 (1981) 201; (b) D. Diaz, J. Robles, T. Ni, S.E. Castillo-Blum, D. Nagesha, O.J.A. Fergoso, N.A. Kotov, J. Phys. Chem. B 103 (1999) 9859; (c) G. Alonso, V. Petranovskii, M. Del Valle, J. Cruz-Reyes, A. LiceaClaverie, S. Fuentes, Appl. Catal. A 197 (2000) 87; (d) C. Zhang, Y. Song, M. Fung, Z. Xued, X. Xin, Chem. Commun. (2001) 843.

3288

M. Hossaini Sadr et al. / Polyhedron 25 (2006) 3285–3288

[4] (a) I. Bezverkhyy, P. Afanasiev, M. Lacriox, Mater. Res. Bull. 37 (2002) 161; (b) S. Shi, Z. Lin, Y. Mo, X.Q. Xin, J. Phys. Chem. 100 (1996) 10696; (c) Y. Liu, J. Chen, M.D. Ryan, Inorg. Chem. 37 (1998) 425. [5] S.H. Laurie, Eur. J. Inorg. Chem. (2000) 2443. [6] (a) J.P. Lang, K. Tatsumi, Inorg. Chem. 37 (1998) 6308, and Refs. [2–8] therein; (b) T. Ecclestone, I. Harvy, S.H. Laurie, M.C.R. Symons, F.A. Taiwo, Inorg. Chem. Commun. 1 (1998) 460; (c) R. Dessapt, C. Simonnet-Jegat, J. Marroy, F. Secheresse, Inorg. Chem. 40 (2001) 4072. [7] (a) K.E. Howard, J.R. Lockemeyer, M.A. Massa, T.B. Rauchfuss, S.R. Wilson, X. Yahg, Inorg. Chem. 29 (1990) 4385; (b) H.G. Zheng, W. Tan, C. Jin, W. Ji, Q. Jin, X. Huang, X.Q. Xin, Inorg. Chim. Acta 305 (2000) 14. [8] (a) D. Shaow, Z. Nianyong, C. Pengcheng, W. Xintao, L. Jiaxi, Polyhedron 11 (1992) 109; (b) D.L. Long, J.T. Chen, J.S. Huang, Inorg. Chim. Acta 285 (1999) 241; (c) M. Hong, D. Wu, R. Cao, X. Lei, H. Liu, J. Lu, Inorg. Chim. Acta 258 (1997) 25; (d) Y. Jeannin, F. Secheresse, S. Bernesa, F. Robert, Inorg. Chim. Acta 198–200 (1992) 493. [9] (a) C. Zhang, G.C. Jin, J.X. Chen, X.Q. Xin, K.P. Qian, Coord. Chem. Rev. 213 (2001) 51; (b) H.W. Hou, X.Q. Xin, S. Shi, Coord. Chem. Rev. 153 (1996) 25; (c) R. Colton, Coord. Chem. Rev. 62 (1985) 145. [10] (a) Q. Liu, Y. Yang, L. Huang, D. Wu, B. Kang, C. Chen, Y. Lu, Inorg. Chem. 34 (1995) 1884; (b) R.J. Salm, A. Misetic, J.A. Ibers, Inorg. Chim. Acta 240 (1995) 239. [11] H.G. Zheng, W. Ji, M.L.K. Low, G. Sakane, T. Shibahara, X.Q. Xin, J. Chem. Soc., Dalton Trans. (1997) 2537. [12] (a) H. Hou, D. Long, X. Xin, X. Huang, B. Kang, P. Ge, W. Ji, S. Shi, Inorg. Chem. 35 (1996) 5363; (b) J.M. Manoli, C. Potvin, Inorg. Chim. Acta 150 (1988) 257. [13] (a) W. Clegg, A. Beheshti, M. Hosaini Sadr, Acta Crystallogr. Sect. E (2002) m349; (b) A. Beheshti, W. Clegg, H. Fallah, Inorg. Chim. Acta 322 (2001) 1. [14] (a) W. Kaim, B. Schwederski, Bioinorganic Chemistry: Inorganic Elements in the Chemistry of Life, Wiley, New York, 1996 (Chapters 10 and 11); (b) E.K. Quagraine, R.S. Reid, J. Inorg. Biochem. 85 (2001) 53. [15] Q. Pan, C.G. Kleer, L.V. Golden, J. Irani, M. Bottema, C. Bias, M.D. Carvalho, E.A. Mesri, D.M. Robin, R.D. Dick, J. Brewer, S.D. Merajver, Cancer Res. 62 (2002) 4854, and Refs. [5–7] therein. [16] K.D. Bissig, T.C. Voegelin, M. Solioz, FEBS Lett. 507 (2001) 367. [17] (a) C. Zhang, Y. Song, Y. Xu, H. Fun, G. Fang, Y. Wang, X. Xin, J. Chem. Soc., Dalton Trans. (2000) 2823; (b) H. Zheng, W. Leung, W. Tan, D. Long, W. Ji, J. Chen, F. Xin, X. Xin, J. Chem. Soc., Dalton Trans. (2000) 2145; (c) S.J. Hibble, M.R. Feaviour, J. Mater. Chem. 11 (2001) 2607; (d) A. Leist, S. Stauf, S.a. Loken, E.W. Finckh, S. Ludtke, K.K. Unger, W. Assenmacher, W. Mader, W. Tremel, J. Mater. Chem. 8 (1998) 241. [18] (a) C. Zhang, Y. Song, X. Wang, F.E. Kuhn, Y. Wang, H. Fun, X. Xin, J. Mater. Chem. 12 (2002) 239; (b) C. Zhang, Y. Song, X. Wang, F.E. Kuhn, Y. Wang, Y. Xue, X. Xin, J. Mater. Chem. 13 (2003) 571; (c) G. Fang, Y. Song, Y. Wang, X. Zhang, C. Li, C. Zhang, X. Xin, Opt. Commun. 181 (2000) 97; (d) Y. Song, C. Zhang, Y. Wang, G. Fang, G. Jin, C. Chang, S. Liu, X. Xin, H. Ye, Chem. Phys. Lett. 326 (2000) 341; (e) Y. Song, C. Zhang, Y. Wang, G. Fang, C. Duan, S. Liu, X. Xin, H. Ye, Opt. Commun. 168 (1999) 131; (f) Y. Song, C. Zhang, X. Wang, Y. Wang, G. Fang, G. Gin, X. Zhan, S. Liu, L. Chen, X. Xin, Mater. Lett. 46 (2000) 49. [19] A. Beheshti, W. Clegg, M. Hosaini Sadr, Polyhedron 20 (2001) 179.

[20] A. Beheshti, W. Clegg, M. Hosaini Sadr, Inorg. Chim. Acta 335 (2002) 21. [21] M. Hossaini Sadr, W. Clegg, H.R. Bijhanzade, Polyhedron 23 (2004) 637. [22] (a) A.G. Sykes, Adv. Inorg. Chem. 36 (1991) 377; (b) E.I. Solomon, K.W. Penfield, D.E.W. Cox, Struct. Bond. 53 (1983) 1. [23] S. Trofimenko, Scorpionates: The Coordination Chemistry of Polypyrazolylborate Ligands, Imperial College Press, London, 1999. [24] (a) S. Trofimenko, Chem. Rev. 93 (1993) 943; (b) S. Trofimenko, Prog. Inorg. Chem. 34 (1986) 115; (c) S. Trofimenko, Acc. Chem. Res. 4 (1971) 17; (d) S. Trofimenko, Inorg. Chem. 1 (1970) 99; (e) S. Trofimenko, J. Am. Chem. Soc. 88 (1966) 1842; (f) S. Trofimenko, J. Am. Chem. Soc. 89 (1967) 3170. [25] (a) C. Slugovc, I.P. Martinez, S. Sirol, E. Carmona, Coord. Chem. Rev. 213 (2001) 129; (b) M.D. Ward, J.A. McCleverty, J.C. Jeffery, Coord. Chem. Rev. 222 (2001) 251; (c) D. Reger, Coord. Chem. Rev. 147 (1996) 571; (d) C. Slugovc, R. Schmid, K. Krichner, Coord. Chem. Rev. 185–186 (1999) 109; (e) S. Hikichi, A. Munetaka, Y. Moro-oka, Coord. Chem. Rev. 198 (2000) 61; (f) N. Marques, A. Sella, J. Takats, Chem. Rev. 102 (2002) 2159. [26] (a) N. Kitajima, W.B. Tolman, Prog. Inorg. Chem. 43 (1995) 419; (b) R.E. Davis, T.A. Dodds, T.H. Hseu, J.C. Wagnon, T. Devon, J. Tancrede, J.S. McKennis, R. Pettit, J. Am. Chem. Soc. 96 (1974) 7565; (c) T.C. Higgs, D.J. Roman, S. Czernuscewicz, C.J. Carrano, Inorg. Chem. Acta 273 (1998) 14; (d) N. Kitajima, K. Fujisawa, C. Fujimoto, Y. Moro-oka, S. Hashimoto, T. Kitagawa, K. Toriumi, K. Tatsumi, A. Nakamura, J. Am. Chem. Soc. 114 (1992) 1277; (e) N. Kitajima, K. Fujisawa, Y. Moro-oka, J. Am. Chem. Soc. 111 (1989) 8975; (f) N. Kitajima, T. Koda, S. Hashimoto, T. Kitagawa, Y. Moro-oka, J. Am. Chem. Soc. 113 (1991) 5664; (g) R. Osterberg, Coord. Chem. Rev. 12 (1974) 309. [27] S. Dhar, P.A.N. Reddy, M. Nethaji, S. Mahadevan, M.K. Saha, A.R. Chakravarty, Inorg. Chem. 41 (2002) 3469. [28] G.M. Sheldrick, SHELXTL: User Manual, Bruker AXS Inc., Madison, WI, USA, 1997. [29] (a) N.R. Brooks, W. Clegg, M. Hossaini Sadr, M. Esm-Hosseini, R. Yavari, Acta Crystallogr., Sect. E 60 (2004) m204; (b) F. Secheresse, S. Bernes, F. Robert, Y. Jeannin, J. Chem. Soc., Dalton Trans. (1991) 2875. [30] (a) M. Hossaini Sadr, S.M. Seyed Ahmadian, N.R. Brooks, W. Clegg, Acta Crystallogr., Sect. E 60 (2004) m1952; (b) J.R. Nicholson, A.C. Flood, C.D. Garner, W. Clegg, J. Chem. Soc., Chem. Commun. (1983) 1179. [31] J. Lapasset, N. Chezeau, P. Belougne, Acat Crystallogr., Sect. B 32 (1976) 3087. [32] G. Alonso, G. Berhault, R.R. Chianlli, Inorg. Chim. Acta 316 (2001) 105. [33] S. Bernes, F. Secheresse, Y. Jeannin, Inorg. Chim. Acta 194 (1992) 105. [34] S. Mandal, G. Das, R. Singh, R. Shukla, P.K. Bharadwaj, Coord. Chem. Rev. 160 (1997) 191. [35] (a) N. Kitajima, Adv. Inorg. Chem. 39 (1992) 18; (b) N. Kitajima, K. Fujisawa, C. Fujimoto, Y. Moro-oka, Chem. Lett. (1989) 421. [36] C. Zhang, Y.L. Song, B.M. Fung, Z.L. Xue, X.Q. Xin, Chem. Commun. (2000) 843. [37] C. Zhang, Y.L. Song, F.E. Ku¨hn, Y.X. Wang, X.Q. Xin, W.A. Herrmann, Adv. Mater. 14 (2002) 818. [38] T. Kawazoe, H. Kawaguchi, J. Inoue, O. Haba, M. Ueda, Opt. Commun. 160 (1999) 125.