Luminescence Thermochromism of Gold(I) Phosphane-Iodide Complexes: A Rule or an Exception?

A series of gold(I) iodide complexes 1-11 have been prepared from di-, tri-, and tetraphosphane ligands. Crystallographic studies reveal that the di- (1-7) and tetrametallic (11) compounds feature linearly coordinated gold(I) ions with short aurophilic contacts. Their luminescence behavior is determined by the combined influence of the phosphane properties, metal-metal interaction, and intermolecular lattice-defined interactions. The proposed variable contribution of 3 (X+M)-centered (X=halogen; M=metal) and 3 XLCT (halogen to ligand charge transfer) electronic transitions into the lowest lying excited state, which is influenced by supramolecular packing, is presumably responsible for the alteration of room-temperature emission color from green (λ=545 nm, for 11) to near-IR (λ=698 nm, for 2). Dinuclear compounds 6 and 7 exhibit distinct luminescence thermochromism with a blueshift up to 5750 cm-1 upon cooling. Such dramatic change of emission energy is assigned to the presence of two coupled triplet excited states of 3 ππ* and 3 (X+M)C/3 XLCT nature, the presence of which depends on both molecular structure and the crystal lattice arrangement.

Cyanide-Assembled d10 Coordination Polymers and Cycles: Excited State Metallophilic Modulation of Solid-State Luminescence.

The series of cyanide-bridged coordination polymers [(P2 )CuCN]n (1), [(P2 )Cu{M(CN)2 }]n (M=Cu 3, Ag 4, Au 5) and molecular tetrametallic clusters [{(P4 )MM'(CN)}2 ]2+ (MM'=Cu2 6, Ag2 7, AgCu 8, AuCu 9, AuAg 10) were obtained using the bidentate P2 and tetradentate P4 phosphane ligands (P2 =1,2-bis(diphenylphosphino)benzene; P4 =tris(2-diphenylphosphinophenyl)phosphane). All title complexes were crystallographically characterized to reveal a zig-zag chain arrangement for 1 and 3-5, whereas 6-10 possess metallocyclic frameworks with different degree of metal-metal bonding. The d10 -d10 interactions were evaluated by the quantum theory of atoms in molecules (QTAIM) computational approach. The photophysical properties of 1-10 were investigated in the solid state and supported by theoretical analysis. The emission of compounds 1 and 3-5, dominated by metal-to-ligand charge transfer (MLCT) transitions located within {CuP2 } motifs, is compatible with thermally activated delayed fluorescence (TADF) behaviour and a small energy gap between the T1 and S1 excited states. The luminescence characteristics of 6-10 are strongly dependent on the composition of the metal core; the emission band maxima vary in the range 484-650 nm with quantum efficiency reaching 0.56 (6). The origin of the emission for 6-8 and 10 at room temperature is assigned to delayed fluorescence. AuCu cluster 9, however, exhibits only phosphorescence that corresponds to theoretically predicted large value ΔE(S1 -T1 ). DFT simulation highlights a crucial impact of metallophilic bonding on the nature and energy of the observed emission, the effect being greatly enhanced in the excited state.

Adjustable coordination of a hybrid phosphine-phosphine oxide ligand in luminescent Cu, Ag and Au complexes.

A potentially tridentate hemilabile ligand, PPh2-C6H4-PPh(O)-C6H4-PPh2 (P(3)O), has been used for the construction of a family of bimetallic complexes [MM'(P(3)O)2](2+) (M = M' = Cu (1), Ag (2), Au (3); M = Au, M' = Cu (4)) and their mononuclear halide congeners M(P(3)O)Hal (M = Cu (5-7), Ag (8-10)). Compounds 1-10 have been characterized in the solid state by single-crystal X-ray diffraction analysis to reveal a variable coordination mode of the phosphine-oxide group of the P(3)O ligand depending on the preferable number of coordination vacancies on the metal center. According to the theoretical studies, the interaction of the hard donor P[double bond, length as m-dash]O moiety with d(10) ions becomes less effective in the order Cu > Ag > Au. 1-10 exhibit room temperature luminescence in the solid state, and the intensity and energy of emission are mostly determined by the nature of metal atoms. The photophysical characteristics of the monometallic species were compared with those of the related compounds M(P(3))Hal (11-16) with the non-oxidized ligand P(3). It was found that in the case of the copper complexes 5-7 the P(3)O hybrid ligand introduces effective non-radiative pathways of the excited state relaxation leading to poor emission, while for the silver luminophores the P[double bond, length as m-dash]O group leads mainly to the modulation of luminescence wavelength.

Tetragold(I) complexes: solution isomerization and tunable solid-state luminescence.

In this study, a new family of tetranuclear gold(I) triphosphine derivatives bearing alkynyl and thiolate groups have been efficiently synthesized by treating the polymeric acetylides (AuC2R)n or a thiolate (AuSPh)n sequentially with the (a) phosphine ligand and (b) cationic complex [Au3(P^P^P)2](3+) (P^P^P = PPh2CH2PPhCH2PPh2). The clusters [Au4(P^P^P)2(C2R)2](2+) [R = Ph (1), biphenyl (2), terphenyl (3), C6H4OMe (4), C6H4NMe2 (5), C6H11O (6), and C6H4CF3 (7)] and [Au4(P^P^P)2(SPh)2](2+) (8) were characterized by X-ray crystallography in the solid state. NMR spectroscopic investigations in solution revealed that the majority of alkynyl clusters 1-7 exist as two isomeric species in slow chemical equilibria. All complexes 1-8 exhibit moderate-to-strong photoemission in the solid state with quantum yields from 0.07 to 0.51. The luminescence behavior was rationalized using quantum chemical density functional theory methods. The high emission efficiency of these tetragold(I) compounds and their good stability in film allowed for the fabrication of an organic electroluminescent device (OLED). Employing complex 5 (Φ = 0.51), an OLED was fabricated under a solution process to give a good external quantum efficiency of 3.1%, corresponding to a current efficiency of 6.1 cd/A and a power efficiency of 5.3 lm/W, with Commission Internationale de I'Eclairage coordinates of (0.52, 0.46).