Series of Near-IR-Absorbing Transition Metal Complexes with Redox Active Ligands

Abstract

New soluble and intensely near-IR-absorbing transition metal (Ti, Zr, V, Ni) complexes were synthesized using a redox non-innocent N,N’-bis(3,5-di-tertbutyl-2-hydroxy-phenyl) -1,2-phenylenediamine (H4L) as a ligand precursor. In all the complexes, ([Ti(Lox)2, [Zr(Lox)2], [V(Lsq1)(HLox)] and [Ni(HLox)2], two organic molecules coordinate to the metal center as tri- or tetradentate ligands. The solid-state structures of the complexes were determined using single crystal XRD, and the compounds were further characterized with Electrospray Ionisation Mass Spectrometry (ESI-MS). Thermoanalytical measurements indicated the thermal stabilities of the complexes. All compounds absorb strongly in the near-IR region and show very interesting magnetic and electrochemical properties. Moreover, it was shown that the V and Ni complexes can also convert absorbed near-IR photons to (un)paired electrons, which indicates great promise in photovoltaic applications.

Pseudo-octahedral nickel(ii) complexes of strongly absorbing benzannulated pincer-type amido ligands: ligand-based redox and non-Aufbau electronic behaviour

“…Compared with other common air-stable transition metal oxidation states, chromophores based on MCCs bearing d 8 Ni( ii ) ions outside of bis-dithiolenes 21 are relatively rare, 22,23 especially those displaying strong NIR absorptions. 24 In a notable example, a pseudo-octahedral Ni( ii ) complex of the non-innocent N , N ′-bis(3,5-di- tert -butyl-2-hydroxy-phenyl)-1,2-phenylenediamine ligand was recently shown to exhibit very strong absorptive cross-sections well into the NIR 25 thanks to the redox-active nature of the ligand. Noting the strengthened absorptive properties enabled by our readily synthesized benzannulated diarylamido ligands, we report here a series of three pseudo-octahedral nickel complexes of phenanthridine/quinoline-based diarlyamido ligands and describe the impact that ligand substitution has on their electronic structures and stabilities upon oxidation.…”

Transparent and photochromic poly(hydroxyethyl acrylate–acrylamide)/WO3 hydrogel with antibacterial properties against bacterial keratitis in contact lens

“…However, due to the redox property of W at different oxidation states, the photons generated NIR are easily transferred by back donation otherwise called metal to ligand charge transfer (MLCT) (Figure 8e). 69 This is so because, the orbitals of WO 3 are readily oxidizable and the orbitals of the C═O are readily reducible with low lying vacant orbitals to receive photons. In essence, the vacant π * molecular orbitals of WO 3 gives rise to strong coloration, while the back‐bonding gives rise to the color fading process.…”

A diamagnetic iron complex and its twisted sister – structural evidence on partial spin state change in a crystalline iron complex

“…However, the reliability of the MOS parameter in describing the oxidation state of a conjugated ligand, such as [HL] n may have issues since such ligands were not included in the MOS parameter set. Therefore, we decided to further compare the bond parameters In three of these the metal ions (V, Mo and W) show oxidation states higher than +2, 6,41,42 whereas in one (Mn) the oxidation state has not been assigned. 43 However, a paramagnetic nickel(II) complex, investigated earlier by us and which is also isostructural with 1, 42 is a suitable comparison.…”