Transition metal complexes of the PPO/POP ligand: variable coordination chemistry and photo-luminescence properties

In the current work the tautomeric equilibrium between tetraphenyldiphosphoxane (Ph₂P-O-PPh₂, POP) and tetraphenyldiphosphine monoxide (Ph₂P-P(O)Ph₂, PPO) in the absence and presence of transition metal precursors is investigated. Whereas with hard transition metal ions, such as Fe(II) and Y(III), PPO-type complexes, such as [FeCl₂(PPO)₂] (1) and [YCl₃(THF)₂(PPO)] (2), are formed, softer transition metals ions tend to form so-called coordination stabilised tautomers of the POP ligand form, such as [Cu₂(MeCN)₃(μ₂-POP)₂](PF₆)₂ (3), [Au₂Cl₂(μ₂-POP)] (4), and [Au₂(μ₂-POP)₂](OTf)₂ (5). The photo-optical properties of the PPO- and POP-type transition metal complexes are investigated experimentally using photo-luminescence spectroscopy, whereby the presence of metallophillic interactions was found to play a crucial role. The dinuclear copper complex [Cu₂(MeCN)₃(μ₂-POP)₂](PF₆)₂ (3) shows a very interesting thermochromic behavior and intense photo-luminescence with remarkable phosphoresence lifetimes at 77 K, which can probably be attributed to short intramolecular Cu-Cu distances.

Structural, spectroscopic and electronic properties of a family of face-shared bi-octahedral Ru25+/6+ complexes with a bridging 2,5-di(2-pyridyl)pyrrolide ligand

Herein, we found that nitrogen donor dpp⁻ligand is flexible and provides a platform for aggregation of Ru²⁺ and/or Ru³⁺ to give a new type of face-sharing bi-octahedra Ru₂⁵⁺ and Ru₂⁶⁺ dimer featuring of distinct metal–metal bond bond between two ruthenium centres.

Complexes of the tripodal phosphine ligands PhSi(XPPh2)3(X = CH2, O): synthesis, structure and catalytic activity in the hydroboration of CO2

The coordination chemistry of Fe²⁺, Co²⁺and Cu⁺ions was explored with the ligands PhSi{CH₂PPh₂}₃(1) and PhSi{OPPh₂}₃(2), so as to evaluate the impact of the electronic properties of the tripodal phosphorus ligands on the structure and reactivity of the corresponding complexes.

Photophysical and electrochemical properties of Ru(II) complexes containing tridentate bisphosphino-oligothiophene ligands

Nine Ru(II) complexes containing the conjugated oligothiophene ligands 3,3''-bis(diphenylphosphino)-2,2':5',2''-terthiophene (P(2)T(3)) and 4',3'''-bis(diphenylphosphino)-3,3''''-dihexyl- 2,2':5',2'':5'',2''':5''',2''''-pentathiophene (P(2)T(5)) were prepared and characterized. P(2)T(3) and P(2)T(5) bond as tridentate ligands and three of the complexes (1, 2 and 5) form green five-coordinate Ru(II) complexes in solution. Cyclic voltammetry, variable temperature UV-vis spectroscopy and time-resolved transient absorption spectroscopy were used to characterize the electronic properties of the complexes. Increased conjugation in the complexes containing the P(2)T(5) ligand resulted in a lowering of the oxidation potential of the oligothiophene, but electropolymerization was not observed. The electronic spectra were dominated by π-π* transitions. All of the complexes were non-emissive both at room temperature and low temperature, indicating the excited state decays by other, non-radiative pathways. The transient absorption spectrum of complex 7 shows a species with a band at 475 nm and a lifetime of ∼100 ns, assigned to a ligand-based triplet state.