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Issue 42, 2013
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Zinc(II), iron(II/III) and ruthenium(II) complexes of o-phenylenediamine derivatives: oxidative dehydrogenation and photoluminescence

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Abstract

Reactions of benzoyl pyridine, o-phenylenediamine and anhydrous ZnX2 in methanol afford imine complexes [Zn(L1)X2] (X = Cl, 1; X = Br, 2) in good yields (L1 = (E)-N1-(phenyl(pyridin-2-yl)methylene)benzene-1,2-diamine). The reduction of 1 with NaBH4 affords (E)-N1-(phenyl(pyridine-2-yl)methylene)benzene-1,2-diamine (L2H). The reaction of L2H with [RuII(PPh3)3Cl2] results in the oxidative dehydrogenation to L1 generating cis-[RuII(L1)(PPh3)Cl2] (3). The reaction of L2H with salicylaldehyde affords (E)-2-(((2-((phenyl(pyridin-2-yl)methyl)amino)phenyl)imino)methyl)phenol (L3H2). The reaction of L3H2 with anhydrous FeCl3 in CH3OH affords cis-[FeIII(L3H)Cl2] (4). Reaction of L3H2 with [RuII(PPh3)3Cl2] results in the oxidative dehydrogenation to diimine, L4H, affording trans-[RuII(L4)(PPh3)2]+, which is isolated as trans-[RuII(L4)(PPh3)2]PF6 (5+PF6) (L4H = 2-((E)-(2-((E)-phenyl(pyridin-2-yl)methyleneamino)phenylimino)methyl)phenol). The reduction of L3H2 with NaBH4 produces 2-(((2-((phenyl(pyridin-2-yl)methyl)amino)phenyl)amino)methyl)phenol (L5H3). With iron(III) L5H3 undergoes oxidative dehydrogenation to L3H2 affording 4, while with [RuII(PPh3)3Cl2], L5H3 undergoes 4e + 4H+ transfer giving 5+. A fluid solution of L3H2 at 298 K exhibits an emission band at 470 nm (λex = 330 nm, τ1 = 3.70 ns) and a weaker band at 525 nm (λex = 330, 390 nm, τ1 = 1.1 ns) at higher concentrations due to molecular aggregation, which are temperature dependent. 4 is brightly emissive (λex = 330 nm, λem = 450 nm, Φ = 0.586, τ1 = 3.70 ns). Time resolved emission spectra (TRES) and lifetime measurements confirm that the lower energy absorption band of L3H2 at 390 nm, which is absent in complex 4, has a larger non-radiative rate constant (knr). The redox innocent AlIII adduct of L3H2 is fluorescent (λex = 330 nm, λem = 450 nm, τ1 = 3.70 ns). On the contrary, the cis-[FeII(L3H)Cl2] and cis-[Co(L3H)Cl2] analogues are non emissive. Density function theory (DFT) calculations, redox potentials and the near infra-red (NIR) absorption data prove that 4 is emissive due to the stable [FeIII(L3H*)] state, while 3, 5+, cis-[FeII(L3H)Cl2] and cis-[Co(L3H)Cl2] are non-emissive due to transformations of the [MII(L*)] to [MIII(L˙*)] states.

Graphical abstract: Zinc(ii), iron(ii/iii) and ruthenium(ii) complexes of o-phenylenediamine derivatives: oxidative dehydrogenation and photoluminescence

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Publication details

The article was received on 02 Jul 2013, accepted on 31 Jul 2013 and first published on 01 Aug 2013


Article type: Paper
DOI: 10.1039/C3DT51771C
Citation: Dalton Trans., 2013,42, 15028-15042
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    Zinc(II), iron(II/III) and ruthenium(II) complexes of o-phenylenediamine derivatives: oxidative dehydrogenation and photoluminescence

    S. Chaudhuri, S. C. Patra, P. Saha, A. Saha Roy, S. Maity, S. Bera, P. Saha Sardar, S. Ghosh, T. Weyhermüller and P. Ghosh, Dalton Trans., 2013, 42, 15028
    DOI: 10.1039/C3DT51771C

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