ABSTRACT
The study of the photophysical properties of dendritic-like phosphinothiolate gold(I) complexes has been carried out. The studied complexes are two series of analogous compounds bearing 4 or 8 metal centers: the tetranuclear [Au(4)(S-C(6)H(4)-X)(4){DAB-G0-(PPh(2))(4)}] (X = F (3), MeO (4), Me (5) and NO(2) (6)) and the octanuclear [Au(8)(S-C(6)H(4)-X)(8){DAB-G1-(PPh(2))(8)}] (X = F (9), MeO (10), Me (11) and NO(2) (12)) complexes. All compounds are brightly luminescent in solid state at 77 K displaying lifetimes in the microsecond range. The correlation between the substituent in position four of the benzenethiolate ligand and the emission energy shows that the emissions arise from (3)[pπ(S)âpσ(Au)] or from intra-ligand (3)[π(S)âπ*(C(6)H(4)X)] charge transfer transitions, depending on the substituents. Theoretical DFT-B3LYP, ONIOM (DFT-B3LYP/UFF) and ONIOM (MP2/UFF) calculations on mononuclear and dinuclear model systems permit evaluation of both the structural distortions upon excitation to the lowest triplet excited state T(1) and the shape of the orbitals involved in the charge transfer transitions. These calculations also allow us to evaluate the influence of the substituent in position four of the benzenethiolate ligand and the presence of Au···Au interactions.
ABSTRACT
[AuAg3(C6F5)(CF3CO2)3(CH2PPh3)]n (2) was prepared by reaction of [Au(C6F5)(CH2PPh3)] (1) and [Ag(CF3CO2)] (1:3). The crystal structures of complexes 1 and 2 were determined by X-ray diffraction, and the latter shows a polymeric 2D arrangement built by Au...Ag, Ag...Ag, and Ag...O contacts. The metallophilic interactions observed in 2 in the solid state seem to be preserved in concentrated THF solutions, as suggested by EXAFS, pulsed-gradient spin-echo NMR, and photophysical studies, which showed that the structural motif [AuAg3(C6F5)(CF3CO2)3(CH2PPh3)] is maintained under such conditions. Time-dependent DFT calculations agree with the experimental photophysical energies and suggest a metal-to-ligand charge-transfer phosphorescence process. Ab initio calculations give an estimated interaction energy of around 60 kJ mol(-1) for each Au...Ag interaction.
ABSTRACT
The reactions of the tetraphosphine ligand DAB-G0-(PPh2)4 (DAB = 1,4-diaminobutane; G0 = Generation 0) or the octaphosphine ligand DAB-G1-(PPh2)8 (G1 = Generation 1) with the gold precursor [AuCl(tht)] (tht =tetrahydrothiophene) and the corresponding 4-substituted benzenethiolate lead to the (phosphine)gold(I) thiolate complexes [Au4(S-C6H4-X)4[(DAB-G0-(PPh2)4]] (X = F (11), MeO (12), Me (13) and NO2 (14)) and [Au8(S-C6H4-X)8[(DAB-G1-(PPh2)4]] (X = F (15), MeO (16), Me (17) and NO2 (18)). Complexes [Au4Cl4[(DAB-G0-(PPh2)4]] and [Au4(S-C6H4-OMe)4[(DAB-G0-(PPh2)4]] have been characterized by X-ray diffraction studies showing tetranuclear gold complexes in which the P-Au-X (X = Cl or S) structural units do not display aurophilic interactions. PGSE NMR studies of free ligands EN-G0-(PPh2)(4) (EN = 1,2-ethylenediamine), DAB-G0-(PPh2)(4), DAB-G1-(PPh2)8 and the (phosphine)gold(I) thiolate complexes permit the evaluation and comparison of the different molecular sizes depending on the ligand and the dendrimer generation.