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