Mono- and bidentate imidates of five-coordinate nickel(ii) with macrocyclic ligands: spectroscopic and photophysical properties

Abstract

The hydroxo-complexes [Ni(2)(mcN(3))(2)(mu-OH)](2)(PF(6))(2)] [mcN(3) = 2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene (Me(3)-mcN(3)) or 2,4,4,9-tetramethyl-1,5,9-triazacyclododec-1-ene (Me(4)-mcN(3))] react with imides (Him) in 1 : 2 (succinimide, glutarimide, saccharine and 1,8-naphthalimide) or 1 : 1 (pyromellitic diimide) molar ratio, leading to the formation of the imidate complexes: [Ni(mcN(3))(H(2)O)(Im)](+) (Im = succi, gluti, sac), [Ni(mcN(3))(naphthi)](+) and [Ni(mcN(3))(H(2)O)](2)(mu-pyrdi)](2+). The single crystal structures of [Ni(Me(3)-mcN(3))(H(2)O)(sac)](PF(6)) (3a) and [Ni(Me(4)-mcN(3))(H(2)O)(sac)](sac) (3b) show that, in 3a, sac exhibits a N-monodentate coordination mode, while in 3b the coordination is through oxygen. X-Ray structure of [Ni(Me(4)-mcN(3))(naphthi)](PF(6)) (4b) shows N,O-bonded 1,8-naphthalimidate ligand. The VT (1)H NMR study, carried out on this complex, suggests that the rotation around the Ni-N bond is hindered by ca. 11.6 kcal mol(-1). These species exhibit blue luminescence which arises from a mixed MLCT and LC excited state, and these properties may be useful for structural predictions in the solid state of complexes for which crystal structures have not been established.

Structural and magnetic properties of dinuclear Cu(II) complexes featuring triazolyl-naphthalimide ligands

“…Bond lengths and angles are consistent with other axially elongated square-based pyramidal structures where the equatorial (square base) bond lengths average 1.985(2) Å whilst the axial bond to the carbonyl oxygen atom is 2.307(2) Å. The coordination of the carbonyl oxygen atoms in naphthalimides to transition metals is not a commonly observed occurrence and only three structures are reported in the CSD [19,41,42]. (Figure 7) with O···centroid distances of 2.881 Å and 2.852 Å for the two different interactions.…”

Nickel Complexes of Pyridine‐Functionalized N‐Heterocyclic Carbenes: Syntheses, Structures, and Activity in Electrocatalytic Hydrogen Production

“…The five‐coordinate geometry of the nickel ion in 1a is not rare; five‐coordinate geometries can be divided into two categories: the trigonal bipyramid and the tetragonal pyramid . The square‐pyramidal geometry is commonly formed with pentadentate chelating ligands, or from a combination of tridentate and bidentate chelating ligands , .…”

Structure and Spectroscopic Properties of Nickel Benzazolate Complexes with Hydrotris(pyrazolyl)borate Ligand

“…Apart from their interest in several applied fields, the synthetic value of nickel group di-μ-hydroxo-complexes is a subject of continuous study . We have contributed to this area by exploiting the usefulness of dinuclear hydroxo-complexes of nickel, some of them with a macrocyclic backbone, in the preparation of a wide variety of new compounds by means of a simple acid–base reaction . In this context, and in line with our interest in studying the photophysical properties of pentacoordinate complexes of nickel(II), in this work we synthesize benzazolate complexes containing the fragment “Ni(Tp*)” (Tp* = hydrotris(3,5-dimethylpyrazolyl)­borate).…”