Deactivation Routes in Gold(I) Polypyridyl Complexes: Internal Conversion Vs Fast Intersystem Crossing

Abstract

An electronic spectral and photophysical characterization of three gold­(I) complexes containing heterocyclic chromophores differing in the number and arrangement of pyridine rings (pyridine, bipyridine, and terpyridine, with the acronyms pD, bD, and tD respectively) was performed. Quantum yields of fluorescence, internal conversion and triplet state formation, together with the rate constants for singlet to triplet intersystem crossing, S1 ∼ ∼ ∼ S0 internal conversion and fluorescence were measured in order to equate the impact of fast triplet state formation on the amount of triplets formed. The results showed a correlation between the increase on the measured decay values of S1 (leading to the main formation of T1) and the increase in the charge transfer (CT) character of the lowest energy transition, as evaluated from the orthogonality of the frontier orbitals. The measured triplet state quantum yields range from ∼50–60% to 70%, whereas the intersystem crossing rate constants differ by almost 2 orders of magnitude, from 9.4 × 109 s–1 for tD to 8.1 × 1011 s–1 for bD. This constitutes an evidence for the existence of a correlation between the intersystem crossing and the internal conversion mechanisms.

Influence of the Attachment of a Gold(I) Phosphine Moiety at the Upper Rim of a Calix[4]pyrrole on the Binding of Tetraalkylammonium Chloride Salts

“…This result is a nice example on how heavy‐atom‐induced spin‐orbital coupling effects can induce luminescence of non‐emissive chromophores, in particular, from metal‐perturbed π–π* excited states localized on aryl‐ethynyl ligands through fast population of the triplet state by intersystem crossing …”

“…This result is an ice example on how heavy-atom-induced spin-orbital coupling effects can induce luminescence of nonemissive chromophores, [27,28] in particular,f rom metal-perturbed p-p*e xcited states localized on aryl-ethynyll igands throughf ast population of the triplet state by intersystem crossing. [29,22] Binding studies of the 10a,20a-bis-aryl-ethynyl calix [4]pyrrole 2w ith tetraalkylammonium chloridesalts 1…”

Effect of Gold(I) on the Room‐Temperature Phosphorescence of Ethynylphenanthrene

“…In comparison with the surrounding metals in the periodic table, gold displays a maximum relativistic effect, which affects the resulting photophysical properties [16–19] . The formation of a gold(I)–carbon σ bond can significantly modify the electronic states of an organic chromophore by enhancing spin‐orbit interactions, thus increasing the rate of intersystem crossing between singlet and triplet states with respect to the free aromatic counterpart [20, 21] . In this way, although only fluorescence emission can be detected for specific organic luminophores, their corresponding organogold(I) compounds can exhibit dual luminescence (fluorescence and phosphorescence) at room temperature with emission yields that depend sensitively on the position of metal coordination [17]…”

Using Room Temperature Phosphorescence of Gold(I) Complexes for PAHs Sensing

“…620 nm) attributed to the phosphorescence of the chromophore [ 12 , 22 , 23 , 39 , 41 ]. The phosphorescence assignment is evidenced by the quenching of the intensity of this emission band in the presence of oxygen ( Figure S10 ) and can be achieved thanks to the presence of the gold(I) heavy atom that favors the intersystem crossing and population of the emissive triplet state [ 42 ]. The heavy atom effect on room temperature phosphorescence of gold(I) naphthalimide complexes is reported herein for the first time although it has previously been observed in platinum complexes, with the similar vibronically structured shape [ 39 ].…”