Gold–heterometal complexes. Evolution of a new class of luminescent materials

Abstract

A very promising area of research in which metallophilic attraction has become the dominating factor determining the structural patterns that give rise to luminescent materials is discussed. In addition to the intrinsic conditions that a gold complex requires to show luminescence, we show how the type and number of the ligands, the coordination environments around the metal centres, the temperature, the heterometal, the metal-metal distances, etc., increase the possibilities of electronic transitions and, hence, multiply the factors that affect the energy and number of emissions. We think that far from being a hindrance or a problem these findings actually give rise to a fascinating area of research with promising future applications, for instance, in imaging technology, vapour sensors, light emitting devices or even medicine, where the demand for optoelectronic devices is increasing every day.

Cupriphication of gold to sensitize d 10 –d 10 metal–metal bonds and near-unity phosphorescence quantum yields

“…2A and 3A). The packing herein for 1 or 3a -notwithstanding the latter's disorder-is similar to that in [Au-C,N-(ethoxy)(p-tolyl)carbeniate] 3 or [Au(μ-3,5-(CF 3 ) 2 Pz)] 3 (13).…”

“…The electronegativity gradient and corresponding orbital mismatch between the Pt(II) and Tl(III) centers lead to a much greater shortening of the M-M′ distances than those allowed by the summed van der Waals radii in the former situation 3.68 Å for Pt(II)-Tl(III) and 3.06 Å for Cu(I)-Au(I) (18,19). A closer example in terms of "softness"/ electrostatic compatibility exists vs. the Tl(I)-Pt(0) polar covalent bonding for [Pt(PPh 2 py) 3 Tl]X complexes, which led to Tl-Pt bond distances of 2.8888(5) and 2.8653(4) Å with X = NO 3 − and C 2 H 3 O 2 − , respectively (20). At the other extreme, we can consider the system AgAu(MTP) 2 (MTP, diphenylmethylenethiophosphinate) described as an Ag(I)⋯Au(I) heterobimetallic argento-aurophilic interaction (as opposed to polar-covalent bonding) type, with a distance of 2.9124(13) Å (21).…”

“…Although the former compound was studied for decades (22,23), the crystal structure of [Au(μ-C 2 ,N 3 -BzIm)] 3 was only recently published; it exhibited a semiprismatic conformation with one long (3.558 Å) and two short (3.346 Å) intertrimer distances to manifest its strong aurophilic interactions (11). The copper precursor for 1-4 has been studied by Dias et al (24) 3 ] that nonetheless represented weaker aurophilic interaction vs. its hexagonal polymorph (27). Even with partial oxidation via organic electron acceptors, some of the aforementioned cyclotrimers exhibited shortened Au⋯Au intertrimer distances that nevertheless remained >3.15 Å (22, 23), which are still much longer than the two 2.8750(8) Å "intertrimer" Cu I -Au I bonds in 4a herein.…”

“…Heterometallic species involving coinage metals have received immense attention owing to their fascinating structural and photophysical properties, including polar-metallophilic interactions and stimulus-responsive luminescence (3)(4)(5)(6)(7)(8)(9). Notable examples include Balch's luminescent Ir-Au-Ir chains (4), Fackler's luminescence-thermochromic Ag I Au I -pyrazolates (7), Catalano's Au-Cu (8), and Laguna's Au-Tl vapochromic sensors (9).…”

“…Heterometallic complexes are remarkable molecules owing to their unique catalytic and optoelectronic properties (2,3). Heterometallic species involving coinage metals have received immense attention owing to their fascinating structural and photophysical properties, including polar-metallophilic interactions and stimulus-responsive luminescence (3)(4)(5)(6)(7)(8)(9).…”