Influence of the Counterion and the Solvent Molecules in the Spin Crossover System [Co(4-terpyridone)2]Xp·nH2O
详细信息 查看全文
- 作者：Ana Galet ; Ana Belé ; n Gaspar ; M. Carmen Muñ ; oz ; and José ; Antonio Real
- 刊名：Inorganic Chemistry
- 出版年：2006
- 出版时间：May 29, 2006
- 年：2006
- 卷：45
- 期：11
- 页码：4413 - 4422
- 全文大小：471K
- 年卷期：v.45,no.11(May 29, 2006)
- ISSN：1520-510X
文摘
A series of new complexes belonging to the [Co(4-terpyridone)2]Xp·nS family (4-terpyridone = 2,6-bis(2-pyridyl)-4(1H)-pyridone) have been synthesized and characterized, using X-ray single crystal determination and magneticsusceptibility studies, to be X = [BF4]- (p = 2) and S = H2O for polymorphs 1 and 2, X = [BF4]- (p = 1) and[SiF6]2- (p = 0.5) and S = CH3OH for 3, X = [SiF6]2- (p = 1) and S = 3CH3OH and H2O for 4, X = [Co(NCS)4]2-(p = 1) and S = 0.5CH3OH for 5, X = I- (p = 2) and S = 5H2O for 6, X = [PF6]- (p = 1) for 7, and X = [NO3]-(p = 2) for 8. Compounds 1-7 can be grouped in three sets according to the space group in which theycrystallize: (i) P
ntities/onemacr.gif"> triclinic (1, 3), (ii) P21 monoclinic (2), and (iii) P21/c monoclinic (4-7). The tridentate 4-terpyridoneligands coordinate the Co(II) ions in a mer fashion defining essentially tetragonally compressed [CoN6] octahedrons.The Co-N axial bonds involving the pyridone rings are markedly shorter than the Co-N equatorial bonds collectivelydenoted as Co-Ncentral and Co-Ndistal, respectively. The differences in the average Co-Ncentral or Co-Ndistal distancesobserved for 1-7 reflect the different spin states of Co(II). Complexes 7 and 4' are fully high spin (HS), while 5 and6 are low spin (LS). However, the counterion [Co(NCS)4]2- in complex 5 is high spin. Complexes 1, 2, 3, and 8exhibit spin-crossover behavior in the 400-100 K temperature region. Compounds 1 and 2 are polymorphs, andinterestingly, 1 irreversibly transforms into 2 above 340 K because of a crystallographic phase transition whichinvolves a drastic modification of the crystal packing. The relevant thermodynamic parameters associated with thespin transition of polymorph 2 have been estimated using the regular solution theory leading to 
H = 3.04 kJmol-1, S = 20 J K-1 mol-1, and ntities/Ggr.gif"> = 0.95 kJ mol-1.
ntities/onemacr.gif"> triclinic (1, 3), (ii) P21 monoclinic (2), and (iii) P21/c monoclinic (4-7). The tridentate 4-terpyridoneligands coordinate the Co(II) ions in a mer fashion defining essentially tetragonally compressed [CoN6] octahedrons.The Co-N axial bonds involving the pyridone rings are markedly shorter than the Co-N equatorial bonds collectivelydenoted as Co-Ncentral and Co-Ndistal, respectively. The differences in the average Co-Ncentral or Co-Ndistal distancesobserved for 1-7 reflect the different spin states of Co(II). Complexes 7 and 4' are fully high spin (HS), while 5 and6 are low spin (LS). However, the counterion [Co(NCS)4]2- in complex 5 is high spin. Complexes 1, 2, 3, and 8exhibit spin-crossover behavior in the 400-100 K temperature region. Compounds 1 and 2 are polymorphs, andinterestingly, 1 irreversibly transforms into 2 above 340 K because of a crystallographic phase transition whichinvolves a drastic modification of the crystal packing. The relevant thermodynamic parameters associated with thespin transition of polymorph 2 have been estimated using the regular solution theory leading to H = 3.04 kJmol-1, S = 20 J K-1 mol-1, and ntities/Ggr.gif"> = 0.95 kJ mol-1.