The photophysical properties of as eries of Tshaped coinage d 10 metal complexes,s upportedb yabis-(mesoionic carbene)carbazolide( CNC) pincerl igand,a re explored. The series includes ar are new example of at ri-dentateT -shaped Ag I complex. Post-complexation modification of the Au I complex provides access to al inear cationic Au I complex following ligand alkylation,o rt he first example of ac ationic square planar Au III ÀFc omplex from electrophilic attack on the metal centre. Emissions ranging from blue (Cu I )t oo range (Ag I )a re obtained, with variable contributionso ft hermally-dependentf luorescencea nd phosphorescence to the observed photoluminescence. Green emissions are observed for all three gold complexes (neutralT -shaped Au I ,c ationic linear Au I and square planar cationic Au III ). The higher quantum yield and longer decay lifetimeo ft he linear gold(I) complex are indicative of increased phosphorescence contribution.In the development of efficient organic light emitting devices (OLEDs), basic requirements of phosphorescente mitters include high externalq uantum efficiencies (EQE) of the emission, coupled with appropriater adiative lifetimes in the ordero fm icroseconds to facilitate the intersystem crossing (ISC) from the triplet to the singlet state. [1] These specifications have been amply met using iridium(III) and platinum(II) emitters, [2] with an increasing number of reports detailing the utility of the lesser explored gold(III) complexes. Indeed, CNC- [3] and CCN- [4] cyclometallated gold(III) complexes excelling in emissioncolor tuning, solubility and thermals tability have recently yielded OLEDsw ith very high EQEs and similarly long device operationalh alf-lifetimes. [4b] Lowero xidation state gold(I), and the other d 10 coinage metals, copper(I) and silver(I), have also been the focus of concurrent investigationsi nto their use in OLEDs. One of the more successful design strategieso nt his front employs the linear bonding geometry of carbene-metal-amides (CMAs),i nw hich all three d 10 metals (Cu I ,A g I and Au I ), have similarly accomplished excellent EQE performance and/or high brightnessO LED operation, notably employing carbazolide derivativesa st he donor amidep artnersw ith the acceptor carbenes. [5] These CMAsc an display particularly short (ns) emission lifetimesi nt hermally assisted delayed fluorescence (TADF), basedo nt he rapid triplet-to-singlet ISC, unlike the heavya tom (metal) phosphorescente mitters relying on spinorbit coupling. [1b, 6] The dependency of photoluminescence on the coordination geometry of d 10 coinage metal complexes is well-known, [7] for example, 3-coordinate trigonal planar copper(I)c omplexes showed tunable behavior from pure phosphorescence to TADF dependingo nt he carbene-metal-amine dihedral angles. [7c] Extending 3-coordinate systemsb eyondt rigonal planar geometries to ag round state Jahn Teller-distorted T-shape has been an early theoretical target for photophysical tuning of the singlet-triplet gap. [8] However,t he availab...

Four homoallyl ortho-vinylaryl ketones (10a-d) -1,8dienes of sorts -were prepared by several approaches. In the presence of 1-2 mol-% Grubbs-II catalyst, they ring-closed to give 6,7-dihydrobenzocyclohepten-5-ones (11a-d) in 90-96 % yield. With SeO 2 the parent compound (11a) delivered benzocyclohepten-5-one (13a) and/or selenium-containing compounds (18)(19)(20)(21)(22) but no more than traces of 6,7-benzotropolone (5a). However, 5a was accessible from compound 11a via the sodium enolate and allowing it to react with a stream of oxygen [a] Scheme 1. Top: our previously established ring-closing olefin metathesis ("RCM")/ketal hydrolysis route to type-5 6,7-benzotropolones. [9] Underneath: regiocomplementary processings of a type-4 RCM product via the dibromide 7 and the bromoolefins 7 or iso-7 by cross-couplings and hydrolyses giving type-8 or type-iso-8 6,7-benzotropolones, respectively. [10] The Arican routes of Scheme 1 have a major drawback, though, namely the harsh conditions required for hydrolyzing a type-4 ketal in the last step: Liberating the enol required refluxing with 10 equiv. of tosic acid and 100 equiv. of water in acetonitrile for 1 h -2 d. [9,10] These conditions were applicable to certain type-9 or type-iso-9-ketals, as well ( Figure 2). When their substituent R was Et, Ph, CO 2 Me or CO 2 Et, such hydrolyses also proceeded well. [9] However, when their substituent R was CH=CH-CO 2 iPr (in 9a or iso-9a), HC=CH 2 (in 9c or iso-9c) or C≡C-SiMe 3 (in iso-9c) the substrate vanished under hydrolysis conditions without delivering any benzotropolone. [9,10] The C≡C-SiMe 3 -containing ketal 9b was an in-between-case: Its hydrolysis released a benzotropolone as expected but the sidechain R had been converted into C(=O)-CH 3 . [10] Eur.2930 Scheme 2. Can 6,7-benzotropolones 5 be reached via an RCM/oxidation route rather than via the RCM/hydrolysis route of Scheme 1? A 4-e 2 oxidation 11 → 5 would be required overall, but two 2-e 2 oxidations 11 → 12 and 12 → 5 might be used as an alternative. 5.We wondered whether step 2 might be disadvantaged vs. a dehydration delivering the benzotropone 13. While 13 looks like a dead-end at first, it might be re-routable towards 5. This is because unsubstituted benzotropone (13, all R = H) gave unsubstituted benzotropolone (5, all R = H) by endoperoxide formation and an ensuing reduction with thiourea. [11] Consequently, benzotropones 13 appeared as conceivable intermediates of our Scheme-2 strategy towards benzotropolones. A Modified Synthesis of 6,7-BenzotropoloneOur proof-of-principle benzotropolone synthesis by the approach of Scheme 1 delivered the parent compound 5a and is shown in Scheme 3 and Scheme 5. Scheme 3 advances to the RCM product and Scheme 5 supplements its oxidation. Scheme 3. Reaching the RCM product 11a, our synthetic precursor of unsubstituted benzotropolone (5a).Our synthesis began by a salt-free Wittig methylidenation of ortho-bromobenzaldehyde (14, Scheme 3). [12] The resulting ortho-bromostyrene (15) was treated sucessively with nBuLi and the...

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The syntheses of bis(triazolium)carbazole precursors and their corresponding coinage metal (Au, Ag) complexes are reported. For alkylated triazolium salts, di‐ or tetranuclear complexes with bridging ligands were isolated, while the bis(aryl) analogue afforded a bis(carbene) AuI‐CNC pincer complex suitable for oxidation to the redox‐stable [AuIII(CNC)Cl]+ cation. Although the ligand salt and the [AuIII(CNC)Cl]+ complex were both notably cytotoxic toward the breast cancer cell line MDA‐MB‐231, the AuIII complex was somewhat more selective. Electrophoresis, viscometry, UV‐vis, CD and LD spectroscopy suggest the cytotoxic [AuIII(CNC)Cl]+ complex behaves as a partial DNA intercalator. In silico screening indicated that the [AuIII(CNC)Cl]+ complex can target DNA three‐way junctions with good specificity, several other regular B‐DNA forms, and Z‐DNA. Multiple hydrophobic π‐type interactions involving T and A bases appear to be important for B‐form DNA binding, while phosphate O⋅⋅⋅Au interactions evidently underpin Z‐DNA binding. The CNC ligand effectively stabilizes the AuIII ion, preventing reduction in the presence of glutathione. Both the redox stability and DNA affinity of the hit compound might be key factors underpinning its cytotoxicity in vitro.

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