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Issue 5, 2017
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The binuclear dual emitter [Br(CO)3Re(P⋯N)(N⋯P)Re(CO)3Br] (P⋯N): 3-chloro-6-(4-diphenylphosphinyl)butoxypyridazine, a new bridging P,N-bidentate ligand resulting from the ring opening of tetrahydrofuran

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Abstract

Lithium diphenylphosphide unexpectedly provokes the ring-opening of tetrahydrofuran (THF) and by reaction with 3,6-dichloropyridazine leads to the formation of the ligand 3-chloro-6-(4-diphenylphosphinyl)butoxypyridazine (P⋯N), which was isolated. The reaction of this ligand with the (Re(CO)3(THF)Br)2 dimer yields the novel complex [Br(CO)3Re(μ-3-chloro-6-(4-diphenylphosphinyl)butoxypyridazine)2Re(CO)3Br] (BrRe(P⋯N)(N⋯P)ReBr), which was crystallized in the form of a chloroform solvate, (C46H40Br2Cl2N4O8P2Re2)·(CHCl3). The monoclinic crystal (P21/n) displays a bimetallic cage structure with a symmetry inversion centre in the middle of the rhenium to rhenium line. The molecule shows two oxidation signals occurring at +1.50 V and +1.76 V which were assigned to the ReI/ReII and ReII/ReIII metal-centered couples, respectively, while signals observed at −1.38 V and −1.68 V were assigned to ligand centered reductions. Experimental and DFT/TDDFT results indicate that the UV-Vis absorption maximum of BrRe(P⋯N)(N⋯P)ReBr occurring near 380 nm displays a metal to ligand charge transfer (MLCT) character, which is consistent with CV results. Upon excitation at this wavelength, a weak emission (Φem < 1 × 10−3) is observed around 580 nm (in dichloromethane) which decays with two distinct lifetimes τ1 and τ2 of 24 and 4.7 ns, respectively. The prevalence of non-radiative deactivation pathways is consistent with efficient internal conversion induced by the high conformational flexibility of the P⋯N ligand's long carbon chain. Measurements in a frozen solvent at 77 K, where vibrational deactivation is hindered, show intense emission associated with the 3MLCT state. These results demonstrate that BrRe(P⋯N)(N⋯P)ReBr preserves the dual emitting nature previously reported for the mononuclear complex RePNBr, with emission associated with Image ID:c6dt04158b-t1.gif and Image ID:c6dt04158b-t2.gif states.

Graphical abstract: The binuclear dual emitter [Br(CO)3Re(P⋯N)(N⋯P)Re(CO)3Br] (P⋯N): 3-chloro-6-(4-diphenylphosphinyl)butoxypyridazine, a new bridging P,N-bidentate ligand resulting from the ring opening of tetrahydrofuran

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Publication details

The article was received on 31 Oct 2016, accepted on 16 Dec 2016 and first published on 16 Dec 2016


Article type: Paper
DOI: 10.1039/C6DT04158B
Citation: Dalton Trans., 2017,46, 1567-1576
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    The binuclear dual emitter [Br(CO)3Re(P⋯N)(N⋯P)Re(CO)3Br] (P⋯N): 3-chloro-6-(4-diphenylphosphinyl)butoxypyridazine, a new bridging P,N-bidentate ligand resulting from the ring opening of tetrahydrofuran

    M. Saldías, J. Manzur, R. E. Palacios, M. L. Gómez, J. D. L. Fuente, G. Günther, N. Pizarro and A. Vega, Dalton Trans., 2017, 46, 1567
    DOI: 10.1039/C6DT04158B

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