From Terminal to Spiro-Phosphonium Acceptors, Remarkable Moieties to Develop Polyaromatic NIR Dyes.

Phosphonium-based compounds gain attention as promising photofunctional materials. As a contribution to the emerging field, we present a series of donor-acceptor ionic dyes, which were constructed by tailoring phosphonium (A) and extended π-NR2 (D) fragments to an anthracene framework. The alteration of the π-spacer of electron-donating substituents in species with terminal -+ PPh2 Me groups exhibits a long absorption wavelength up to λabs =527 nm in dichloromethane and shifted the emission to the near-infrared (NIR) region (λ=805 nm for thienyl aniline donor), although at low quantum yield (Φ<0.01). In turn, the introduction of a P-heterocyclic acceptor substantially narrowed the optical bandgap and improved the efficiency of fluorescence. In particular, the phospha-spiro moiety allowed to attain NIR emission (797 nm in dichloromethane) with fluorescence efficiency as high as Φ=0.12. The electron-accepting property of the phospha-spiro constituent outperformed that of the monocyclic and terminal phosphonium counterparts, illustrating a promising direction in the design of novel charge-transfer chromophores.

Improved synthetic routes to N-heterocyclic carbene-metal-diketonato complexes of gold and copper.

In our search for simple synthetic routes to N-heterocyclic carbene (NHC)-metal complexes and their derivatives, we herein report an operationally simple, expedient and scalable method to obtain the widely used NHC-metal-diketonates. The reported complexes are synthesized for the first time under mild, aerobic conditions and in excellent yields in a sustainable manner. The protocol is general with regards to the anionic co-ligand and the ancillary carbene ligands. The spectroscopic and crystallographic characterization of the complexes reveal a bidentate binding mode of the diketonate ligand to copper while the gold-congener is C-bound. Finally, the reported Au complex was shown to be an efficient pre-catalyst for the hydrocarboxylation of alkynes.

Synthesis of Carbene-Metal-Amido (CMA) Complexes and Their Use as Precatalysts for the Activator-Free, Gold-Catalyzed Addition of Carboxylic Acids to Alkynes.

A straightforward synthetic protocol leading to carbene-metal-amido (CMA) complexes (metal=Au, Cu) using a mild base and an environmentally desirable solvent (EtOH) has been explored, with a focus on complexes bearing backbone-substituted N-heterocyclic carbene (NHC) ligands, including BIAN-NHCs (BIAN=bis(imino)acenaphthene). The novel CMAs were structurally characterized, and gold-based CMAs bearing diverse NHCs were screened as simple, Brønsted-basic precatalysts. The readily accessible complexes display high catalytic activity in the intermolecular and intramolecular hydrocarboxylation of internal alkynes and alkynoic acids respectively, while the screening reveals the ancillary ligand effect of NHCs in these catalytic systems.

Straightforward synthesis of [Cu(NHC)(alkynyl)] and [Cu(NHC)(thiolato)] complexes (NHC = N-heterocyclic carbene).

Synthetic access to monomeric copper-alkynyl and copper-thiolato complexes of the type [(NHC)Cu(R)] (R = alkynyl or thiolato) using a weak base approach is reported. All reported reactions proceed under mild conditions in air and in environmentally acceptable solvents. The novel complexes are fully characterized and single crystal X-ray analyses unambiguously establish the atom connectivity in these mononuclear complexes. The importance of the supporting NHC ligand's steric properties in stabilizing mononuclear complexes is discussed.