Pol ish J. Chem., 81, 1567 1575 (2007) Hy dro ther mal Syn the sis, Struc ture Char ac ter iza tion of a New Mixed Mo/V Metal-Ox y gen Clus ter Com pound: [Co(phen) 3 ] 2 [HPMo 4 V Mo 4 VI V 6 IV M 2 O 44 ] 4H 2 O, (M = 0.78Mo V + 0.22V IV ) by Y.-H. Sun 1,3, X.-P. Li 3, D.H. Sun 3, L. Niu 1* and J.-Q. Xu 2 1 State Key Lab o ra tory of Electroanalytical Chem is try, Changchun In sti tute of Ap plied Chem is try, Chi nese Acad emy of Sci ences, Changchun, 130022, P.R. China *e-mail: lniu@ciac.jl.cn 2 College of Chemistry and State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin Uni ver sity, Changchun, 130023, P.R. China 3 De part ment of Chem is try, Baicheng Teacher s Col lege, Baicheng, Jilin, 137000, P.R. China (Re ceived March 29th, 2007; re vised manu script May 31st, 2007) A new polyoxometalate [Co(phen) 3 ] 2 [HPMo 4 V Mo 4 VI V 6 IV M 2 O 44 ] 4H 2 O (M = 0.78Mo V + 0.22V IV ) 1 was hy dro ther mally syn the sized and char ac ter ized by IR, el e men tal anal y ses, X-ray pho to elec tron spec trum, ESR and sin gle crys tal X-ray dif frac tion. The ti tle com - pound is in the triclinic space group P1 with a = 12.0953(7), b = 14.0182(6), c = 14.6468(7), V = 2402.55(18) 3, = 105.134(2), = 91.841(3), = 91.401(2), Z = 1, and R 1 (wr 2 ) = 0.0617 (0.1701). The com pound was pre pared from tetra-capped pseudo-keggin with phos pho rus-cen tered polyoxoanions [PMo 8 V 6 M 2 O 44 ] 5, [Co(phen) 3 ] 2+ cat ions and linked through hy dro gen bonds and - stack ing in ter ac tion into three-di men sional supra mo lecu lar frame work. A study of the mag netic prop er ties of 1 dem on strates that it ex hib its antiferromagnetic cou pling in ter ac tions. Key words: hydrothermal synthesis, polyoxometalate, crystal structure, transition metal, cobalt Polyoxometalates have at tracted a great in ter est for a long time ow ing to their var i ous interesting to pol o gies to be ma nip u lated in a ra tio nal fash ion, partly be cause of their po ten tial use ful elec tronic, op ti cal, cat a lytic and mag netic prop er ties with im mense im por tance [1 7]. De spite the fun da men tal and prac ti cal im por tance of polyoxometalates, the prep a ra tion of these com plexes still re mains elu sive and is of - ten de scribed as self-as sem bly. It is there fore vi tal to de sign and syn the size novel POMs with dif fer ent struc tural char ac ter is tics in or der to ex plore their prop er ties. In the last few years, one of the im por tant ad vances in tran si tion metalate chem is try has been the study of cap ping struc tural polyoxoanions and closed host cage struc tural metal-ox y gen clus ter com pounds (a small guest is in the host shell). To our know - ledge, in con trast to an ex ten sive lit er a ture on Keggin and tran si tion metal sub sti tuted Keggin spe cies struc tural in for ma tion re lat ing to capped Keggin struc tures is very * Author for correspondence. Fax: (+86)431-526-2800
1568 Y.-H. Sun et al. lim ited due to the lack of good qual ity sin gle crys tals and suit able preparation meth - ods. It has been re cently dem on strated that the hy dro ther mal tech nique is well suited for the prep a ra tion and crys tal growth of mixed Mo/V heteropoly com pounds [8 15]. As a part of our work aimed at ra tio nal de sign and prep a ra tion of func tional supra mo lecu lar com pounds, we car ried out a study of polyoxomatalate de riv a tives. In this pa per, we re port the hy dro ther mal syn the sis, crys tal struc ture and mag ne tism of new polyoxometalates: [Co(phen) 3 ] 2 H[PMo 4 V Mo 4 VI V 6 IV M 2 O 44 ] 4H 2 O 1. EX PER I MEN TAL Ma te ri als and mea sure ments. All re agents were pur chased com mer cially and used with out fur ther pu ri fi ca tion. In fra red spec trum com pound was re corded with Perkin-Elmer Spec trum One spectro - photometer in the 225 4000 cm 1 re gion us ing a pow dered sam ple in a KBr plate. The el e men tal anal y sis was de ter mined us ing a Perkin Elmer 2400 Se ries II CHNS/O el e men tal an a lyzer. In duc tively cou pled plasma (ICP) anal y sis was con ducted on a Perkin Elmer Op tima 3300DV spec trom e ter. De ter mi na tion of elec tron spin res o nance (ESR) was car ried out on Bruker ER 200D-SRC spec trom e ter. XPS anal y sis was per formed on a VG ESCALAB MK II spec trom e ter with a Mg-K (1253.6 ev) ach ro matic X-ray source. Flu o res cent mea sure ment was per formed on FS900 Eding Burgh in stru ments. Vari able tem per a ture mag - netic sus cep ti bil ity mea sure ments for 1 were per formed on a Quan tum De sign MPMS XL-5 SQUID magnetometer in 4 300 K. Hy dro ther mal syn the sis. Com pound 1 was syn the sized as black block crys tals in 62% yield based on Mo by us ing hy dro ther mal method. A mix ture of NH 4 VO 3 (0.3 g), H 2 MoO 4 (0.4 g), CoCl 2 (0.3 g), H 3 PO 4 (0.1 ml), 1,10-phenanthroline (0.5 g) and H 2 O (18 ml) was neu tral ized to ph = 6.0 with NH 3 H 2 O un der con tin u ous stir ring and then sealed in a 30 ml Tef lon-lined au to clave, which was heated to 170 C for three days. Af ter slow cool ing to room tem per a ture, black block crys tals of 1 were sep a rated. Anal. Calcd. for C 72 H 57 Mo 9.56 N 12 Co 2 O 48 PV 6.44 : C, 26.56; H, 1.75; N, 5.16. Found: C, 26.55; H, 1.72; N, 5.16. IR (KBr, cm 1 ) for 1: 3426s, 3065s, 1623m, 1584m, 1516w, 1424w, 1341m, 1302m, 1256s, 1222m, 1144m, 1104m, 1074m, 1051, 947w, 866m, 858m, 722w, 641m, 590m, 519m. X-Ray crys tal log ra phy. Sin gle crys tal struc ture de ter mi na tion by X-ray dif frac tion was per formed on a Siemens SMART CCD diffractometer with Mo-K ra di a tion at 293 K. The struc ture so lu tion and re - fine ments were car ried out us ing SHELXL 97. The struc ture was solved us ing Patterson meth ods and all of the non-hy dro gen at oms were lo cated from ini tial so lu tion or from sub se quent elec tron den sity dif fer - ence maps dur ing the ini tial stages of the re fine ment. All of the non-hy dro gen at oms in the struc ture were re fined us ing anisotropic ther mal dis place ment pa ram e ters. Hy dro gen at oms were treated as ide al ized con tri bu tions. Mo5 and V are crys tal lo graphi cally dis or dered with oc cu pancy fac tors of 0.78 and 0.22, re - spec tively. Se lected crys tal lo graphic data and struc ture de ter mi na tion pa ram e ters for 1 are given in Ta ble 1. The se lected bond lengths for 1 are listed in Ta ble 2. RESULTS AND DIS CUS SION Struc ture de scrip tion. A sin gle crys tal X-ray anal y sis re veals that 1 con sists of an un usual tetra-capped pseudo-keggin with phos pho rus-cen tered polyoxoanion [PMo 4 V Mo 4 VI V 6 IV M 2 O 44 ] 5 (M = 0.78Mo V + 0.22V IV ), [Co(phen) 3 ] 2+ cat ion and lat - tice wa ter (Fig. 1).
Hy dro ther mal syn thesis, structure characterization of a new mixed... 1569 Ta ble 1. Crys tal data and struc ture re fine ment for 1. Empirical formula C 36 H 28.5 Mo 4.78 N 6 CoO 24 P 0.5 V 3.22 For mula weight 1626.4 Tem per a ture 293(2) K Wave length 0.71073 Crys tal sys tem, space group Triclinic, P1 Unit cell di men sions a = 12.1351(5) = 105.134(2) b = 14.0182(6) = 91.841(3) c = 14.6468(7) = 91.401(2) Vol ume 2402.55(18) 3 Z, Calc (mg m 3 ) 2, 2.248 Ab sorp tion co ef fi cient 2.245 mm 1 F(000) 1575 Crystal size 0.211 0.198 0.175 mm range for data col lec tion 2.17 to 25.21 Limiting indices 12 h 14, 16 k 16, 14 l 17 Re flec tions col lected/unique 13659/8560 [R int = 0.0887] Com plete ness to = 25.21 98.7% Re fine ment method Full-ma trix least-squares on F 2 Data/re straints/pa ram e ters 8560/1/701 Good ness-of-fit on F 2 1.116 Fi nal R in di ces [I >2 (I)] R 1 = 0.0617, wr 2 = 0.1701 R in di ces (all data) R 1 = 0.0647, wr 2 = 0.1729 Larg est diff. peak and hole 1.746 and 1.586 e 3 Ta ble 2. Se lected bond lengths [ ] for com pound 1. Co(1) N(4) 2.107(7) Mo(5) O(16) 1.616(6) Co(1) N(5) 2.110(8) Mo(5) O(19) 1.976(7) Co(1) N(2) 2.141(8) Mo(5) O(20) 1.983(6) Co(1) N(6) 2.142(7) Mo(5) O(18)#1 2.000(6) Co(1) N(3) 2.153(8) Mo(5) O(22)#1 2.026(6) Co(1) N(1) 2.163(7) V(1) O(9) 1.627(6) Mo(1) O(17) 1.670(6) V(1) O(23) 1.942(6) Mo(1) O(5) 1.856(7) V(1) O(22) 1.944(6) Mo(1) O(6) 1.877(7) V(1) O(21) 1.948(7) Mo(1) O(21) 1.979(7) V(1) O(18) 1.961(7) Mo(1) O(18) 2.004(6) V(2) O(7) 1.605(6) Mo(2) O(12) 1.653(7) V(2) O(20) 1.921(6) Mo(2) O(6) 1.865(7) V(2) O(19) 1.924(6) Mo(2) O(13) 1.879(6) V(2) O(24) 1.970(6) Mo(2) O(24)#1 1.978(6) V(2) O(8) 1.983(7) Mo(2) O(19)#1 1.999(7) V(3) O(15) 1.6823(10) Mo(3) O(11) 1.672(6) V(3) O(23) 1.956(7)
1570 Y.-H. Sun et al. Ta ble 2 (con tin u a tion) Mo(3) O(13) 1.856(7) V(3) O(24) 1.968(7) Mo(3) O(10) 1.856(7) V(3) O(8) 1.975(7) Mo(3) O(23)#1 1.973(6) V(3) O(21) 1.976(7) Mo(3) O(22)#1 2.000(6) V(3) O(3) 2.389(10) Mo(4) O(14) 1.663(7) V(3) O(2)#1 2.395(10) Mo(4) O(5) 1.868(7) P(1) O(4) 1.485(10) Mo(4) O(10) 1.868(7) P(1) O(3) 1.530(11) Mo(4) O(8) 1.977(7) P(1) O(2) 1.565(10) Mo(4) O(20) 1.997(6) P(1) O(1) 1.566(10) Sym me try code: #1 x + 1, y + 1, z + 1 Fig ure 1. View of crys tal struc ture of 1. The polyoxoanion [PMo 4 V Mo 4 VI V 6 IV M 2 O 44 ] 5 (M = 0.78Mo V + 0.22V IV ) is based on well-known -Keggin struc ture with four ad di tional five-co or di nated ter mi nal VO 2+ units to form hexadecametal host shell [Mo 8 V 6 M 2 O 40 ] 2 and there is a dis or - dered PO 4 3 an ion in side this host shell as a guest. The PO 4 tet ra he dron has P O dis - tances of 1.485(10) 1.566(10) and bond an gles in the range of 107.4(5) 112.3(5). This host cage is con structed from six VO 5 and two MO 5 square pyr a mids by shar ing square edges to form a cen tral belt and two Mo 4 rings bonded above and be low this V 6 M 2 belt (Fig. 2). Each MoO 5 also ex hib its square py ram i dal con fig u ra tion. In each
Hy dro ther mal syn thesis, structure characterization of a new mixed... 1571 Mo 4 ring, four MoO 5 square pyr a mids are linked each other through four 2 -O at oms, while their other non-ter mi nal ox y gen at oms are shared with neigh bor ing VO 5 square pyr a mids in the V 6 M 2 cen tral belt. The Mo O and V O bond lengths are in the range of Mo O t 1.616(6) 1.672(6), Mo O b 1.856(7) 2.026(6), V O t 1.605(6) 1.682(10), V O b 1.921(6) 1.983(7), re spec tively. In the cat ion [Co(phen) 3 ] 2+, each Co 2+ cat ion is co or di nated by three bidentate 1,10- phenan - throline lig ands to form dis torted octahedron with Co N bond length of 2.107(7) 2.163(7). It is worth not ing that the polyoxometalate de riv a tive ex hib its an in ter est ing 3-D supra mo lecu lar frame work as shown in Fig. 3. The three phenan - throline groups of each cat ion ex tend along dif fer ent di rec tion, and through - stack ing in ter ac tion be tween phenanthroline groups with con tact dis tances of 3.657(6), 3.572(5) and 3.522(5), re spec tively, the cat ions are con nected each other to form 2-D supra mo lecu lar lay ers in ac plane (Fig. 4). The polyoxoanions [PMo 4 V Mo 4 VI V 6 IV M 2 O 44 ] 5 are ex actly de pos ited be tween two cat ion lay ers to form the poly - oxoanion lay ers, and the cat ions linked the polyoxoanions through hy dro gen bond - ing be tween the car bon at oms of phenanthroline and the ter mi nal ox y gen at oms of polyoxoanion, the in ter atomic dis tances and an gles re gard ing some of the stron gest hy dro gen bond ing (C H O) are listed in Ta ble 3. These hy dro gen bond ing and - stack ing in ter ac tions in clud ing edge-to-face ar o matic C H in ter ac tion force the struc ture of 1 to ex tend into an in ter est ing 3-D supra mo lecu lar ar ray. Fig ure 2. Poly he dral rep re sen ta tion of the struc ture of [PMo 4 V Mo 4 VI V 6 IV M 2 O 44 ] 5. The as sign ment of the ox i da tion state for the V and Mo at oms is con sis tent with the elec tric charge and con firmed by bond va lence sum cal cu la tions. The BVS val ues for V(1) V(3) are 3.9, 4.09 and 3.6, re spec tively, in di cat ing that the ox i da tion state for all the V at oms is +4. The cal cu lated va lence sum for Mo(1) Mo(5) are 5.38, 5.46, 5.45, 5.42 and 5.03, re spec tively [16], in di cat ing the Mo at oms are in the mixed va - lence state.
1572 Y.-H. Sun et al. Fig ure 3. View of crys tal pack ing of ti tle com pound along a axis. Fig ure 4. The - stack ing in ter ac tion of cat ions of 1. Ta ble 3. Lengths of C H O hy dro gen bonds ( ) and an gles ( ) for the ti tle com pound. C25 H25 154.61(0) 3.338(5) O11 [x, y, z] C33 H33 104.11(0) 3.038(3) O7 [ 1 + x, 1 + y, z] C15 H15 153.72(0) 3.261(5) O11 [1 x, 1 y, 2 z] C34 H34 140.23(0) 3.246(3) O9 [1 x, y, 1 z] C22 H22 150.53(0) 3.100(5) O17 [1 x, y, 1 z] C29 H29 153.03(0) 3.165(5) O17 [ 1 + x, y, z] C9 H9 137.62(0) 3.175(5) O16 [x, 1 + y, z] ESR and XPS spec trum. The ESR spec trum of com pound 1 (Fig. 5) at room tem per a ture only shows a V 4+ sig nal with g = 1.96, which is con sis tent with the re sult of va lence sum cal cu la tions. In the XPS for 1, (Sup ple men tary ma te rial), we ob serve one peak at 515.5 ev, at trib ut able to V 4+ 2P 3/2, and four over lapped peaks at 230.9,
Hy dro ther mal syn thesis, structure characterization of a new mixed... 1573 g = 1.96 1000 2000 3000 4000 5000 6000 7000 G Fig ure 5. The ESR spec trum of the ti tle com pound. 232.6, 234.2 and 236.0 ev, be ing as cribed to Mo 5+ 3d 5/2, Mo 5+ 3d 3/2, Mo 6+ 3d 5/2 and Mo 6+ 3d 3/2, re spec tively. This re sult fur ther con firms that Mo at oms are in mixed va - lences state. XPS spec trum ex hib its one peak at 781.4 ev, at trib uted to Co 2+ 2p 3/2 (see sup ple men tary ma te rial). Flu o res cent prop er ties. Com pound 1 emit ted strong blue lu mi nes cence upon ex ci ta tion with 340 nm, and their strong emis sion bands are at max = 400 nm with a shoul der at ca. 383 nm (Fig. 6). To un der stand the na ture of the two emis sion bands, the photoluminescence prop er ties of the 1,10-phenanthroline lig ands were an a lyzed and the strong emis sion peak for the 1,10-phenanthroline at 400 nm with a shoul der at ca. 383 nm ( ex = 340 nm) (in sert in Fig. 6) was ob tained, which is at trib ut able to the * tran si tion. There fore, the two emis sion bands of com pound 1 re sulted from the * tran si tion of the ligand. These ob ser va tions in di cate that compound 1 ex hib its strong flu o res cent emis sion and may be an ex cel lent can di date for po ten tial photo - active ma te ri als. intensity (a.u.) 383 400 intensive (a.u.) 383 400 400 500 600 700 wavelength (nm) 400 450 500 550 wavelength/nm Fig ure 6. Photoluminescent spec tra of 1 in the DMF so lu tion at am bi ent tem per a ture. In sert shows photoluminescent spec tra of 1,10-phenanthroline in the DMF so lu tion at am bi ent tem per a ture.
1574 Y.-H. Sun et al. Mag netic prop er ties. The vari able tem per a ture mag netic sus cep ti bil ity of 1 was mea sured from 4 to 300 K at 1000 Oe. The ther mal vari a tions of eff and 1/ m of 1 are dis played in Fig. 7. The plot of eff ver sus T shows a eff value of 6.22 B at 300 K and ex hib its a con tin u ous de crease on cool ing to a value of 4.81 B at 4 K. This be hav ior of the eff curve in di cates that there ex ists antiferromagnetic ex change in ter ac tion in 1. The eff value (6.22 B ) at 300 K is lower than the spin-only value ex pected for a sum of two S = 3/2 spin of Co(II) ions, four S = 1/2 spins of Mo 5+ and six S = 1/2 spins of V 4+ at oms ( eff = 9.16 B as sum ing g = 2.0 for Mo 5+ and V 4+ and g = 2.68 for Co 2+ ) [17], in di cat ing antiferromagnetic cou pling. Sim i lar trends have also been ob served in other high-nuclearity spin polyoxometalate clus ters [17 19]. Un for tu nately, it is too dif fi cult to fit the ex per i men tal mag netic data of this heterometallic high nucle - arity spin sys tem by us ing a suit able the o ret i cal model. How ever, the mag netic data of sam ple 1 obeys Cu rie-weiss law in the high-tem per a ture re gion and fit ting in the range 50 300 K gives value of C = 5.08 emu K mol 1 and = 6.62 K, char ac ter is tic of an over all antiferromagnetic in ter ac tion. 70 m -1/ emu -1 mol 60 50 40 30 20 10 0 0 50 100 150 200 250 300 T / K 6 eff / B 5 Fig ure 7. The ef fec tive mag netic mo ment eff and in verse mo lar sus cep ti bil ity vs. tem per a ture for com pound 1. Sup ple men tary data: Crys tal lo graphic data for the struc tures re ported in this ar ti cle have been de - pos ited in the Cam bridge Crys tal lo graphic Data Cen tre, CCDC No. 235446. Cop ies of this in for ma tion may be ob tained free of charge from the di rec tor, CCDC, 12 Un ion Road, Cam bridge CB2 1EZ, UK (Fax: +44-1223-336033; e-mail: de posit@ccdc.cam.ac.uk) or also from the au thor Li Niu. Acknowledgments This work was sup ported by the Na tional Sci ence Foun da tion of China (No. 20475053 and No. 20673109), De part ment of Sci ence and Tech nol ogy of Jilin Prov ince (No. 20050102) and Min is try of Sci ence and Tech nol ogy of China (No. 2006BAKB05).
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