861402-06-4Relevant articles and documents
A new family of luminescent compounds: Platinum(II) imidoylamidinates exhibiting pH-dependent room temperature luminescence
Sarova, Ginka H.,Bokach, Nadezhda A.,Fedorov, Alexander A.,Berberan-Santos, Mario N.,Kukushkin, Vadim Yu.,Haukka, Matti,Da Silva, Joao J. R. Frausto,Pombeiro, Armando J. L.
, p. 3798 - 3805 (2006)
The imidoylamidinate platinum(II) compounds [Pt{NH=C(R)NC(Ph)=NPh} 2] (R = CH2Ph 2, p-ClC6H4 3, Ph 4) were prepared by the reaction of the appropriate trans-[PtCl 2(RCN)2] with 4 equiv of the amidine PhC(=NH)NHPh giving 2-4 and 2 equivs of the salt PhC(=NH)NHPh·HCl. We also synthesized, by the double alkylation of 4 with MeOSO2CF3, complex [Pt{NH=C(Ph)N(Me)C(Ph)=NPh}2][CF3SO3] 2 (5) which models the bis-protonated form of 4. The complexes were characterized by 1H, 13C NMR, and IR spectroscopies, FAB-MS and by C, H, N elemental analysis. The X-ray crystallography of 4·2CH2Cl2 enables the confirmation of the square planar coordination geometry of the metal center with almost planar imidoylamidine ligands, while in 5·2CHC3 the planarity of the metallacycles is lost and and the central N atom is sp3-hybridized. The imidoylamidinate complexes represent a new family of Pt(II)-based luminescent complexes and they are emissive at room temperature both in solution and in the solid state, with an emission quantum yield ranging from 3. 7 × 10-4 to 6.2 × 10-2 in methanol solution; the emission intensity is pH-dependent, being quenched at low pH. UV-visible and luminescence spectroscopies indicate that the lowest excited state of these compounds is 3MLCT or 3IL with significant MLCT character, with emission lifetimes of a few μs. A blue shift of both the absorption and emission with increasing solvent polarity and with decreasing π-electron withdrawing properties of the ligand substituent was observed. The Royal Society of Chemistry 2006.
Nitrile-amidine coupling at Pt(IV) and Pt(II) centers. An easy entry to imidoylamidine complexes
Bokach, Nadezhda A.,Kuznetsova, Tatyana V.,Simanova, Svetlana A.,Haukka, Matti,Pombeiro, Armando J. L.,Kukushkin, Vadim Yu.
, p. 5152 - 5160 (2008/10/09)
Treatment of trans-[PtCl4(RCN)2] (R = Me, Et, Ph, NEt2) with 2 equiv of the amidine PhC(=NH)NHPh in a suspension of MeCN (R = Me), CHCl3 (R = Et, Ph), or in CHCl3 solution (R = NEt2) results in the formation of the imidoylamidine complexes trans-[PtCl4{NH=C(R)N=C(Ph)NHPh}2] (1-4) isolated in good yields (66-84%). The reaction of soluble complexes 3 and 4 with 2 equiv of Ph3P=CHCO2Me in CH2Cl2 (40°C, 5 h) leads to dehydrochlorination resulting in a chelate ring closure to furnish the platinum(IV) chelates [PtCl2{NH=C(R)NC(Ph)=NPh}2] (R = Ph, 5; R = NEt2, 6), accordingly, and the phosphonium salt [Ph 3PCH2CO2Me]Cl. Treatment of 5 with 3 equiv of Ph3P=CHCO2-Me at 50°C for 5 d resulted in only a 30% conversion to the corresponding Pt(II) complex [Pt{NH=C(NEt2)NC-(Ph)= NPh}2] (15). The reduction can be achieved within several minutes, when Ph2PCH2CH2PPh2 in CDCl 3 is used. When the platinum(II) complex trans-[PtCl 2(RCN)2] is reacted with 2 equiv of the amidine, the imidoylamidinato complexes [PtCl(RCN){NH=C(R)NC(Ph)=NHPh}] (8-11) and [PhC(=NH)NHPh]·HCl (7) are formed. The reaction of trans-[PtCl 2(RCN)2] with 4 equiv of the amidine under a prolonged reaction time or treatment of [PtCl(RCN)-{NH=C(R)NC(Ph)=NHPh}] (8-11) with 2 more equiv of the amidine yields the complex bearing two chelate rings [Pt{NH=C(R)NC(Ph)=NHPh}2] (12-15). The treatment of cis-[PtCl 2(RCN)2] (R = Me, Et) with the amidine gives ca. 50-60% yield of [PtCl2{NH=C(R)NHC(Ph)=MHPh}] (16 and 17). All of the platinum compounds were characterized by elemental analyses; FAB mass spectrometry; IR spectroscopy; 1H, 13C{1H}, and 195Pt NMR spectroscopies, and four of them (4, 6, 8, and 15) were also characterized by X-ray crystallography. The coupling of the Pt-bound nitriles and the amidine is metal-mediated insofar as RCN and PhC(=NH)NHPh do not react in the absence of the metal centers in conditions more drastic than those of the observed reactions. The nitrile-amidine coupling reported in this work constitutes a route to the synthesis of imidoylamidine complexes, some of them exhibiting luminescent properties.
