Structural control in Cu(II) coordination polymers through the conformational flexibility of a 2,3-dipyridyl ketone oxime ligand

Abstract

Four new compounds prepared from the ligand 2,3-dipyridyl ketone oxime (L ²³ ) with varying Cu(II) salts were synthesised and structurally characterised, {[Cu(L ²³ )(L ²³ -H)](ClO₄)}_∞ (1), {[Cu(L ²³ )(L ²³ -H)](BF₄)¼(H₂O)}_∞ (2), [Cu₃(L ²³ -H)₂(L ²³ ′)(NO₃)₂OH]₂(NO₃)₂(C₃H₈O)₆ (3) and [Cu(L ²³ )Cl₂]_∞ (4). The effects of differing counterions, as well as the rotational conformational versatility of L ²³ , were demonstrated by the differing polymeric structures that were observed. Complex 1 and 2 both existed as 1-D polymeric chains with L ²³ acting as a pseudo-tetradentate ligand through an oxime–oximato bridge. Complex 1 formed a helical arrangement while 2 formed a chiral chain with both 1 and 2 exhibiting similar chiral packing. Complex 3 formed an unusual inverse–9–metallacrown–3 complex, with one of the L ²³ ligands in a zwitterionic form. Complex 4 was present as a simple 1-D meso-helical chain.

Keywords:

• dipyridyl ketone oxime
• coordination-polymer
• inverse-9-metallacrown-3 copper triangle
• oxime–oximato
• chiral propeller

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Tertiary Education Commission New Zealand for the award of a Top Achiever Doctoral Scholarship (VJA) and the University of Otago Research Committee (VJA) and the University of Otago are thanked for financial support.