Turning a “useless” ligand into a “useful” ligand: a magneto-structural study of an unusual family of Cu^II wheels derived from functionalised phenolic oximes

Abstract

While the phenolic oximes (R-saoH2) are well known for producing monometallic complexes of the type [M(II)(R-saoH)2] with Cu(II) ions in near quantitative yield, their derivatisation opens the door to much more varied and interesting coordination chemistry. Here we show that combining the complimentary diethanolamine and phenolic oxime moieties into one organic framework (H4L1 and H4L2) allows for the preparation and isolation of an unusual family of [Cu(II)]n wheels, including saddle-shaped, single-stranded [Cu(II)8] wheels of general formula [Cu8(HL1)4(X)4](n)[Y] (when n = 0, X = Cl(-), NO3(-), AcO(-), N3(-); when n = 2+ X = (OAc)2/(2,2'-bpy)2 and Y = [BF4]2) and [Cu8(HL2)4(X)4] (X = Cl(-), Br(-)), a rectangular [Cu6(HL1)4] wheel, and a heterometallic [Cu4Na2(HL1)2(H2L1)2] hexagon. Magnetic studies show very strong antiferromagnetic exchange between neighbouring metal ions, leading to diamagnetic ground states in all cases. DFT studies reveal that the magnitude of the exchange constants are correlated to the Cu-N-O-Cu dihedral angles, which in turn are correlated to the planarity/puckering of the [Cu(II)]n rings.

A review on oxime functionality: an ordinary functional group with significant impacts in supramolecular chemistry

“…69,77 The oxime derivative Oxm-53 formed octametallic Cu(II) wheels through a straight forward reaction with copper(II) salts, as well as a single-stranded hexametallic mixed-metal Na 2 Cu 4 wheel. 78 Among mixed metal wheels, the hexametallic Na 2 Cu 4 wheel of compound Oxm-53 is the earliest example that has been reported. In a similar manner, oxime Oxm-54 generated heterometallic complexes with Zn(II) and Ln(III) 79 metal ions as well as dodecametallic Mn(III) wheels.…”

Magneto–structural maps and bridged-ligand effect for dichloro-bridged dinuclear copper(ii) complexes: a theoretical perspective

“…In this study we estimated J calc using a broken-symmetry density functional theory (BS-DFT) method proposed by Noodleman et al 47,48 that is effective for estimating J for various dinuclear and polynuclear complexes. [49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67] Detailed technical discussion regarding J calc via BS-DFT for dinuclear and trinuclear complexes is available. 49,[51][52][53][54][63][64][65][66][67] Calculations were performed using ORCA 5.0.3 soware 68,69 using the def2-TZVPP basis set.…”

“…[49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67] Detailed technical discussion regarding J calc via BS-DFT for dinuclear and trinuclear complexes is available. 49,[51][52][53][54][63][64][65][66][67] Calculations were performed using ORCA 5.0.3 soware 68,69 using the def2-TZVPP basis set. 70,71 Structural optimizations were performed by the M06-2X method.…”

Magneto‐structural correlations of oximato‐bridged dinuclear copper(II) complex: A theoretical perspective

“…The density functional theory combined with the broken symmetry approach (DFT‐BS) by Noodleman et al [40, 41] was used to evaluate J values. This method is well‐established for estimating the magnetic coupling constants for various dinuclear and multicore complexes [42–64]. In this study, all calculations were performed in ORCA 5.0.3 software [65, 66], using a tight SCF convergence (1 × 10 −8 Eh in energy).…”