A Class of Luminescent Cyclometalated Alkynylgold(III) Complexes:  Synthesis, Characterization, and Electrochemical, Photophysical, and Computational Studies of [Au(C^∧N^∧C)(C⋮CR)] (C^∧N^∧C = κ³C,N,C Bis-cyclometalated 2,6-Diphenylpyridyl)

Abstract

A new class of luminescent cyclometalated alkynylgold(III) complexes, [Au(RC=N(R')=CR)(CCR' ')], i.e., [Au(C=N=C)(C triple bond CR'')] (HC=N=CH = 2,6-diphenylpyridine) R' ' = C6H5 1, C6H4-Cl-p 2, C6H4-NO2-p 3, C6H4-OCH3-p 4, C6H4-NH2-p 5, C6H4-C6H13-p 6, C6H13 7, [Au(tBuC=N=CtBu)(C triple bond CC6H5)] 8 (HtBuC=N=CtBuH = 2,6-bis(4-tert-butylphenyl)pyridine), and [Au(C=NTol=C)(CCC6H4-C6H13-p)] 9 (HC=NTol=CH = 2,6-diphenyl-4-p-tolylpyridine), have been synthesized and characterized. The X-ray crystal structures of most of the complexes have also been determined. Electrochemical studies show that, in general, the first oxidation wave is an alkynyl ligand-centered oxidation, while the first reduction couple is ascribed to a ligand-centered reduction of the cyclometalated ligand with the exception of 3 in which the first reduction couple is assigned as an alkynyl ligand-centered reduction. Their electronic absorption and luminescence behaviors have also been investigated. In dichloromethane solution at room temperature, the low-energy absorption bands are assigned as the pi-pi* intraligand (IL) transition of the cyclometalated RC=N(R')=CR ligand with some mixing of a [pi(C triple bond CR'') --> pi*(RC=N(R')=CR)] ligand-to-ligand charge transfer (LLCT) character. The low-energy emission bands of all the complexes, with the exception of 5, are ascribed to origins mainly derived from the pi-pi* IL transition of the cyclometalated RC=N(R')=CR ligand. In the case of 5 that contains an electron-rich amino substituent on the alkynyl ligand, the low-energy emission band was found to show an obvious shift to the red. A change in the origin of emission is evident, and the emission of 5 is tentatively ascribed to a [pi(CCC6H4NH2) --> pi*(C=N=C)] LLCT excited-state origin. DFT and TDDFT computational studies have been performed to verify and elucidate the results of the electrochemical and photophysical studies.

Multiaddressable molecular rectangles with reversible host–guest interactions: Modulation of pH-controlled guest release and capture

“…pH-sensitive pyridine moieties have, therefore, been incorporated into the backbone of the rectangle to modulate the reversible host-guest interaction within the constrained rectangle environment on protonation/deprotonation of the pyridine nitrogen atom to achieve multiaddressable functions that would not have been readily achievable with the molecular tweezers structure. Additionally, the use of various platinum and gold complexes as guest molecules, which have been shown to display anticancer therapeutic behavior (58)(59)(60)(61)(62)(63)(64)(65), may lead to the design of a smart multiaddressable molecular rectangle system that could capture and release specific guest molecules under different pH conditions to achieve proof-ofprinciple on-demand controlled drug delivery. Herein, the design and synthesis of a series of alkynylplatinum(II) terpyridine molecular rectangles ( Fig.…”

Synthesis of Stable Gold(III) Pincer Complexes with Anionic Heteroatom Donors

“…Coordination compounds of gold(III) are valuable in medicine, 1 materials science, 2 and catalysis. 3 Despite the utility of this high-valent metal, gold(III) remains underexplored in comparison to gold(I), due in part to the propensity of gold(III) complexes to undergo decomposition via reduction 4 and protodemetalation.…”

Generation of Nucleophilic Chromium Acetylides from gem‐Trichloroalkanes and Chromium Chloride: Synthesis of Propargyl Alcohols

“…[29] Aromatic aldehydes 12a – d and 12g – i bearing diverse, sensitive functional groups such as bromo, cyano, acetoxy, methoxy, and fluoro, were well tolerated and afforded expected adducts 3a– d [30,31] and 3g–i [32] in good to excellent yields (Table 1, Entries 1–4, 7–9). Similarly, an α,β-unsaturated aldehyde like ( E )-cinnamaldehyde (12f) reacted smoothly and delivered cleanly the corresponding propargyl allyl alcohol 3 f [30] in a good isolated yield of 63% (Table 1, Entry 6).…”