摘要:
An unusual (CuSCN)¥ structural motif in the non-centrosymmetric coordination polymer [(CuSCN)2(pyrimidine)]¥ ¥ Introduction The rapid development of coordination polymer chemistry over recent years has been fuelled by the potential applications that this area of crystal engineering promises.1 Amongst those materials which have begun to realise some of this potential are those which exhibit non-linear optical properties, most noticeably second harmonic generation.2 All of the applications that have been suggested for coordination networks, including host–guest chemistry,3 unusual electronic4 and magnetic5 properties as well as NLO characteristics,2 arise because of the possibility of high levels of design that can be incorporated into the polymeric structure using the now well understood building-block methodology.As with other areas of crystal engineering6 the synthesis of non-centrosymmetric coordination polymers that may exhibit non-linear optical properties is a significant challenge. We have begun to investigate the properties of pyrimidine as simple inspection of the literature reveals that a significant proportion of the coordination polymers prepared using this non-centrosymmetric ligand crystallise in noncentrosymmetric space groups, in contrast to the behaviour of many other pyridyl based bridging ligands.7 Sarah A. Barnett, Alexander J. Blake, Neil R. Champness* and Claire Wilson School of Chemistry, The University of Nottingham, University Park, Nottingham, UK NG7 2RD.E-mail: Neil.Champness@nottingham.ac.uk Received 21st January 2000, Accepted 14th February 2000, Published 21th February 2000 The coordination network [(CuSCN)2(pym)]¥ (pym = pyrimidine) has been prepared and characterised by single crystal X-ray diffraction studies, revealing a new three-dimensional (CuSCN)¥ structural motif. The pyrimidine ligands are arranged such that the resultant coordination network is non-centrosymmetric. formation of (CuS)¥ chains, which are arranged in planes, which run alternately in the [101] and [–101] directions. The N-donor of each SCN– links to a third Cu(I) centre, such that each SCN– ligand adopts a (m2S, m1N) bridging mode. The thiocyanate bridging links the (CuS)¥ chains resulting in the formation of a three-dimensional (CuSCN) lattice (Fig.2) which is constructed from linked 12- and 18- membered rings (Fig. 3). Both the 12- and 18-membered rings are spanned by pyrimidine ligands. The pyrimidine ligands bisect the 12-membered rings in the (CuSCN)¥ array bridging Cu(I) centres to afford shorter 10-membered rings (Fig. 4). The larger 18-membered rings are similarly spanned by pyrimidine ligands generating an alternative ring, which includes a Cu(I) centre which was not a member of the 18-membered ring generated within the (CuSCN)¥ network (Fig. 4). Coincidentally this new, pyrimidine containing circuit is also 18-membered. Fig. 1 A view of the copper coordination environment observed in [(CuSCN)2(pym)]¥ showing the numbering scheme adopted (displacement ellipsoids are drawn at the 50% probability level) [symmetry codes: (i) 1/4 + x, 1/4 – y, 1/4 + z; (ii) –x, 1/2 – y, 1/2 + z; (iii) –x, –y, +z].Selected bond lengths (Å) and angles (°) Cu1– N1 = 2.069(5); Cu1–S1S = 2.3528(16); Cu1–S1Si = 2.4549(15); Cu1–N1Sii = 1.921(5) Å; N1Sii–Cu1–N1 = 115.9(2); N1Sii–Cu1– S1S = 118.7(2); N1Sii–Cu1– N1–Cu1–S1S = 104.76(13); S1Si = 113.76(16); N1–Cu1–S1Si = 98.94(14); S1S–Cu1– S1Si = 102.18(6). [Cu—light blue; S—yellow; N—blue]. Results and discussion Addition of pyrimidine in methanolic solution to CuSCN dissolved in a 2 M aqueous ammonia solution, in either a 1 : 1 or 1 : 2 reaction stoichiometry, affords the coordination polymer [(CuSCN)2(pym)]¥ (pym = pyrimidine) as a yellow precipitate that is insoluble in all common solvents.† Single crystals, of suitable quality for X-ray diffraction studies, were prepared in a similar manner by leaving the reaction mixture to stand for up to a week.The X-ray structure determination (Table 1) of [(CuSCN)2(pym)]¥ reveals that the compound exists as a three-dimensional coordination network in which a (CuSCN)¥ three-dimensional array is essentially impregnated by bridging pyrimidine ligands. Each Cu(I) centre is coordinated by two sulfur donors from two thiocyanate ligands, one N-donor from a third thiocyanate group and one pyrimidine N-donor (Fig. 1). Each S-donor of any given thiocyanate bridges two Cu(I) ions resulting in the CrystEngComm, 2000, 5Table 1 Crystal data for [Cu2(SCN)2(pyrimidine)]¥a Properties Formula MCrystal system Space group a/Å b/Å c/Å U/Å3 ZF(000) Dc /g cm–3 m (Mo-Ka)/mm–1 qmax/° Tmin Tmax Unique reflections (Rint) 514 (0.0535) Reflections I > 2 s (I) Weighting scheme w–1 P [max(Fo2,0) + 2Fc2]/3 R1 [I >2 s (I)]15 0.0335 (65 parameters) wR2 [all data]15 0.0822 (65 parameters) S 1.13 ( D/ s)max <0.001 D rmax/eÅ–3 1.02 Flack parameter 0.00(3) a Click here for full crystallographic data (CCDC no.1350/11). A yellow sphenoid (0.38 � 0.36 � 0.35 mm3) was used for data collection on a Stoe Stadi- 4 four-circle diffractometer (graphite monochromated Mo-Ka radiation, w – q scans). The structure was solved using direct methods16 and all non-H atoms were located using subsequent difference-Fourier methods.16 Hydrogen atoms were placed in calculated positions and were allowed to ride on their parent atoms.Interestingly the pyrimidine ligands are all arranged within the extended structure such that the C3 fragments of these molecules, their "tails", are oriented in the same [001] direction (Fig. 5) affording a system which crystallises in the non-centrosymmetric space group Fdd2. The (CuSCN)¥ array observed here is unique. Within the coordination chemistry of CuSCN several polymeric structural types have been observed including onedimensional chains, stair-polymer structures8,9 and twodimensional sheets,9–11 observed in the closely related compound [(CuSCN)2(pyrazine)]¥ which is constructed with the linear analogue of pyrimidine, pyrazine (Scheme 1).To our knowledge the compound reported here represents the first example of a complex in which the polymeric CuSCN framework forms a three-dimensional arrangement. CuSCN itself adopts two polymorphic three-dimensional arrays12 which are both quite different from that observed here. Indeed the closest parallels are to the structure observed in the pyridinium salt of the anionic framework {[Cu2(SCN)3]}¥13 in which the three-dimensional (CuSCN)¥ framework is templated around the pyridinium cations. In the structure reported here it may be considered that the (CuSCN)¥ array is indeed moulded, or templated, around the pyrimidine ligands. The CuSCN framework is also quite unusual in another respect.The majority of coordination polymers are propagated by a combination of the connectivity of the metal centre and the divergent nature of the ligands used.1 In this case the three-dimensional nature of the coordination Data C6H4Cu2N4S2 323.33 Orthorhombic Fdd2 (no. 43) 12.560(3) 18.943(4) 8.136(2) 1935.7(7) 81264 2.219 4.783 26.08 0.183 0.278 494 s2(Fo2) + (0.0583 P)2 polymer is independent of the role of the ligand which does not contribute to the overall dimensionality of the product. Although one and two-dimensional polymeric fragments are relatively common for the metal-bearing unit,8–11,14 to our knowledge this is the first example where this component of the network is three-dimensional.It proved possible to prepare bulk samples of [(CuSCN)2(pym)]¥ and comparison of their powder X-ray diffraction pattern with that simulated from the single crystal X-ray studies confirmed that the structure outlined above was indeed consistent with the bulk precipitate. IR studies of CuSCN complexes can be informative, confirming the coordination mode of the SCN– anion within the coordination network. In the case of [CN)2(pym)]¥ the nC–N stretch is observed at 2126 cm–1; this is consistent with the (m2S, m1N) bridging mode observed in the crystal structure and compares favourably with the analogous nC–N bands observed for the complexes [(CuSCN)2(pyrazine)]¥ (2123 cm–1),9,10 [(CuSCN)2(4,4’- bipyridyl)]¥ (2129 cm–1)9 and [(CuSCN)(pyridine)]¥ (2120 cm–1)11 all of which contain a similar SCN– structural unit and exhibit similar coordination at the Cu(I) centre.In conclusion we have further illustrated the propensity of the bridging ligand pyrimidine to generate non-centrosymmetric coordination polymers. In this example the X-ray structure of [(CuSCN)2(pym)]¥ reveals that the pyrimidine ligands are arranged such that their "tails" are oriented in a polar manner, leading to the framework’s non-centrosymmetric nature.(a) Fig. 2 (a) View of the extended (CuSCN)¥ lattice observed in [(CuSCN)2(pym)]¥. [Cu—light blue (cross-hatched); S—yellow (right-hatched); N—blue (dotted)]. (b) Click image or here to access a 3D representation of the (CuSCN)¥ framework. (a) Fig.3 (a) View of the 12- and 18-membered (CuSCN)n rings observed in [(CuSCN)2(pym)]¥. [Cu—light blue (cross-hatched); S—yellow (righthatched); N—blue (dotted)]. (b) Click image or here to access a 3D representation. (a) Fig. 4 (a) View of the "extended" copper coordination environment observed in [(CuSCN)2(pym)]¥, illustrating the way in which the pyrimidine bridging ligands span the rings of the three-dimensional (CuSCN)¥ network. [Cu—light blue (cross-hatched); S—yellow (right-hatched); N— blue (dotted)]. (b) Click image or here to access a 3D representation. (b) (b) (b)(a) (b) Fig. 5 (a) A view of the [(CuSCN)2(pym)]¥ coordination network illustrating the orientation of the C3 "tails" of the pyrimidine ligands and thus the non-centrosymmetric nature of the compound.[Cu—green (cross-hatched); S—yellow (right-hatched); N—blue (dotted)]. (b) Click image or here to access a 3D representation of the extended structure of [(CuSCN)2(pym)]¥. Scheme 1 Polymeric arrangements of CuSCN previously observed in coordination compounds (a) chain, (b) stair-polymer, (c) two-dimensional sheet.8–11 [Cu—light blue; S—yellow; N— blue; C—black]. We thank the EPSRC for support. References 1 S. R. Batten and R. Robson, Angew. Chem., Int. Ed., 1998, 37, 1460; A. J. Blake, N. R. Champness, P. Hubberstey, W-S. Li, M. Schröder and M. A. Withersby, Coord. Chem. Rev., 1999, 183, 117; M. Munakata, L. P. Wu and T. Kuroda-Sowa, Adv. Inorg. Chem., 1998, 46, 173; O. M. Yaghi, H. Li, C. Davis, D.Richardson and T. L. Groy, Acc. Chem. Res., 1998, 31, 474; P. J. Hagrman, D. Hagrman and J. Zubieta, Angew. Chem., Int. Ed., 1999, 38, 2638. 2 W. B. Lin, Z. Y. Wang and L. Ma, J. Am. Chem. Soc., 1999, 121, 11249; O. R. Evans, R. G. Xiong, Z. Y. Wang, G. K. Wong and W. B. Lin, Angew. Chem., Int. Ed., 1999, 38, 536; W. B. Lin, O. R. Evans, R. G. Xiong and Z. Y. Wang, J. Am. Chem. Soc., 1998, 120, 13272; R-G. Xiong, J-L. Zuo, X-Z. You, H-K. Fun and S. S. S. Raj, New. J. Chem., 1999, 23, 1051. 3 B. F. Abrahams, P. A. Jackson and R. Robson, Angew.Chem., Int. Ed., 1998, 37, 2657; D. M. L. Goodgame, D. A. Grachvogel and D. J. Williams, Angew. Chem., Int. Ed., 1999, 38, 153; C. J. Kepert and M. J. Rosseinsky, Chem. Commun., 1999, 375.4 C. N. R. Rao, A. Ranganathan, V. R. Pedireddi and A. R. Raju, Chem. Commun., 2000, 39. 5 F. Lloret, G. De Munno, M. Julve, J. Cano, R. Ruiz and A. Caneschi, Angew. Chem., Int. Ed., 1998, 37, 135. 6 D. Braga, F. Grepioni and G. R. Desiraju, Chem. Rev., 1998, 98, 1375. 7 K. Nakayama, T. Ishida, R. Takayama, D. Hashizume, M. Yasui, F. Iwasaki and T. Nogami, Chem. Lett., 1998, 497; S. W. Keller, Angew. Chem., Int. Ed. Engl., 1997, 36, 247; C. V. K. Sharma and R. D. Rogers, Cryst. Eng., 1998, 1, 19; H. Cai, H-M. Hu, W-Z. Chen, H-G. Zhu and X-Z. You, Chem. Lett., 1999, 221. 8 P. C. Healy, C. Pakawatchai, R. Papasergio, V. A. Patrick and A. H. White, Inorg. Chem., 1984, 23, 3769; P. C. Healy, B. W. Skelton, A. F. Waters and A. H. White, Aust.J. Chem., 1979, 32, 1049. 9 A. J. Blake, N. R. Brooks, N. R. Champness, M. Crew, L. R. Hanton, P. Hubberstey, S. Parsons and M. Schröder, J. Chem. Soc., Dalton Trans., 1999, 2813. 10 A. J. Blake, N. R. Champness, M. Crew, L. R. Hanton, S. Parsons and M. Schröder, J. Chem. Soc., Dalton Trans., 1998, 1533. 11 H. Krautshied, N. Emig, N. Klaasen and P. Seringer, J. Chem. Soc., Dalton Trans., 1998, 3071. 12 M. Kabesova, M. Dunaj-Jurco, M. Serátor, J. Gazo and I. Garja, Inorg. Chim. Acta, 1976, 17, 161; D. L. Smith and V. I. Saunders, Acta Crystallogr., Sect. B, 1982, 38, 907. 13 C. L. Raston, B. Walter and A. H. White, Aust. J. Chem., 1979, 32, 2757. 14 A. J. Blake, N. R. Brooks, N. R. Champness, P. A. Cooke, A. M. Deveson, D. Fenske, P. Hubberstey, WS. Li and M. Schröder, J. Chem. Soc., Dalton Trans., 1999, 2103; A. J. Blake, N. R. Brooks, N. R. Champness, P. A. Cooke, M. Crew, A. Deveson, L. R. Hanton, P. Hubberstey, D. Fenske and M. Schröder, Cryst. Eng., 1999, 2, 181; A. J. Blake, N. R. Brooks, N. R. Champness, L. R. Hanton, P. Hubberstey and M. Schröder, Pure Appl. Chem., 1998, 70, 2351. 15 G. M. Sheldrick, SHELXL-97, University of Göttingen, Germany, 1997. 16 G. M. Sheldrick, SHELXS-97, University of Göttingen, Germany, 1997. Paper b000590h Footnote † Experimental: [(CuSCN)2(pyrimidine)]¥. CuSCN ( 33 mg, 2.70 mmol) was dissolved in degassed dilute aqueous NH3 (60 cm3) and a solution of pyrimidine (108 mg, 1.35 mmol) in methanol (5 cm3) was added. The solution became slightly blue and a yellow solid was precipitated overnight. Yield 13%. (Found: C, 21.86; H, 1.19; N, 16.42. Calc. for C6H4Cu2N4S2: C, 22.29; H, 1.25; N, 17.33%.) IR (KBr)/cm–1: 2897w, 2891w, 2126s, 1585s, 1464m, 1395s, 1220w, 1171w, 1074m, 894w, 808w, 763m, 704m, 656w, 446w. CrystEngComm © The Royal Society of Chemistry 2000
ISSN:1466-8033
DOI:10.1039/b000590h
出版商:RSC
年代:2000
数据来源: RSC