Structural, EPR, and Electrochemical Studies of Binuclear Copper(II) Complexes of Bis(pentadentate) Ligands Derived from Bis(1,4,7-triazacyclonane) Macrocycles
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- 作者：Suzanne J. Brudenell ; Leone Spiccia ; Alan M. Bond ; Peter Comba ; and David C. R. Hockless
- 刊名：Inorganic Chemistry
- 出版年：1998
- 出版时间：July 27, 1998
- 年：1998
- 卷：37
- 期：15
- 页码：3705 - 3713
- 全文大小：337K
- 年卷期：v.37,no.15(July 27, 1998)
- ISSN：1520-510X
文摘
Structural, electrochemical, and EPR studies of binuclear copper(II) complexes of bis(pentadentate) ligands, obtainedby attaching 2-pyridylmethyl arms to the four secondary nitrogens of bis(tacn) macrocycles linked by ethyl (tmpdtne,[Cu2(tmpdtne)](ClO4)4·2H2O 2), propyl (tmpdtnp, [Cu2(tmpdtnp)](ClO4)4 3), butyl (tmpdtnb, [Cu2(tmpdtnb)](ClO4)44), m-xylyl (tmpdtnm-X, [Cu2(tmpdtnm-X)](ClO4)4·2DMSO·2H2O, 5), and 2-propanol (tmpdtnp-OH, [Cu2(tmpdtnp-OH)](ClO4)4·2H2O, 6) bridges, are reported, together with further analysis of the mononuclear complex, [Cu(dmptacn)](ClO4)2 1, dmptacn = 1,4-bis(2-pyridylmethyl)-1,4,7-triazacyclononane. Single-crystal X-ray diffractionstudies established the molecular structure of 3 and the tetrakis(DMF) solvate of 4. Complex 3 crystallizes in themonoclinic space group P21/c (No. 14) with a = 13.867(3), b = 13.548(6), c = 28.055(4) Å, 
= 102.63(1)
, V= 5143(2) Å3, and Z = 4. Refinement gave R = 0.085 and Rw = 0.089 for 3696 observed reflections. 4 crystallizesin the triclinic space group 
acr.gif"> (No. 2) with a = 11.775(4), b = 12.718(3), c = 13.201(3) Å, 
= 61.25(2), =75.99(3), 
= 77.66(3), V = 1673(1) Å3, and Z = 1. Refinement gave R = 0.072 and Rw = 0.065 for 3876observed reflections. In 4, the pentadentate compartments are oriented in an anti configuration, while in 3,constraints introduced by the propane bridging group result in a syn configuration. Both complexes exhibit distortedsquare pyramidal (SP) geometries about the Cu(II) centers with Cu-N(apical) 
2.25 Å and Cu-N(equatorial) 2.0 Å. Molecular mechanics calculations have been carried out on these types of complexes for the first timein order to predict the solution structures of 5 and 6. The calculations revealed that the SP geometry is alsopreferred by these complexes and that there is little energy difference between the syn and anti configurations.Cyclic, square-wave, and steady-state voltammetric studies on 1-6 indicate that, on the time scale of themeasurements, 1 undergoes a one-electron reduction to the Cu(I) state while 2-6 undergo an overall two-electronreduction to the binuclear Cu(I) complexes. For 2-4, a shift in reduction potential to more negative values withincreasing Cu···Cu separation reflects the stabilization of the Cu(II) state while the two partially resolved reductionprocesses for 6 suggest that the alcohol group in the ligand backbone promotes a small level of interaction betweencopper centers.
= 102.63(1), V= 5143(2) Å3, and Z = 4. Refinement gave R = 0.085 and Rw = 0.089 for 3696 observed reflections. 4 crystallizesin the triclinic space group acr.gif"> (No. 2) with a = 11.775(4), b = 12.718(3), c = 13.201(3) Å, = 61.25(2), =75.99(3), = 77.66(3), V = 1673(1) Å3, and Z = 1. Refinement gave R = 0.072 and Rw = 0.065 for 3876observed reflections. In 4, the pentadentate compartments are oriented in an anti configuration, while in 3,constraints introduced by the propane bridging group result in a syn configuration. Both complexes exhibit distortedsquare pyramidal (SP) geometries about the Cu(II) centers with Cu-N(apical) 2.25 Å and Cu-N(equatorial) 2.0 Å. Molecular mechanics calculations have been carried out on these types of complexes for the first timein order to predict the solution structures of 5 and 6. The calculations revealed that the SP geometry is alsopreferred by these complexes and that there is little energy difference between the syn and anti configurations.Cyclic, square-wave, and steady-state voltammetric studies on 1-6 indicate that, on the time scale of themeasurements, 1 undergoes a one-electron reduction to the Cu(I) state while 2-6 undergo an overall two-electronreduction to the binuclear Cu(I) complexes. For 2-4, a shift in reduction potential to more negative values withincreasing Cu···Cu separation reflects the stabilization of the Cu(II) state while the two partially resolved reductionprocesses for 6 suggest that the alcohol group in the ligand backbone promotes a small level of interaction betweencopper centers.