364729-56-6Relevant articles and documents
The effects of distal ligand substitution on the copper(II)/ bis-(2,6-dipyrazol-1-ylpyridine) centre
Solanki, Nayan K.,Leech, Michael A.,McInnes, Eric J.L.,Zhao, Jing P.,Mabbs, Frank E.,Feeder, Neil,Howard, Judith A.K.,Davies, John E.,Rawson, Jeremy M.,Halcrow, Malcolm A.
, p. 2083 - 2088 (2001)
The complex [Cu(L4)2](BF4)2 (3; L4 = 2-[pyrazol-1-yl]-6-[3-{2,4,6-trimethylphenyl}pyrazol- 1-yl]pyridine) has been synthesised. Complex 3 crystallises in two crystal forms from MeNO2/Et2O. The monoclinic α-form contains crystallographically ordered, pseudo-Jahn-Teller elongated {dy2-z2}1 Cu(II) ions that are structurally very similar to [CH(L2)2](BF4)2 (1; L2 = 2,6-dipyrazol-1-ylpyridine). The Cu ion in the orthorhombic β-polymorph at 180 K exhibits Cu-N bond lengths that are rather different from the α-form, and which could correspond to a disordered {dy2-z2}1 Cu(II) centre; or, to a static, rhombically compressed ion with a {dz2}1 ground state. Variable temperature EPR data favour the former interpretation. A crystal structure at 31 K of [Cu(L3)2](BF4)2 (2; L3 = 2,6-bis-[3-{2,4,6-trimethylphenyl}pyrazol-1-yl]pyridine), a genuine {dz2}1 ion, is also described. Comparison of the crystallographic data of 1-3 shows that the {dy2-z2}1-to-{dz2} 1 ground state change occurs concomitantly with only a small z-axis compression.
