FRET Sensitization of Tungsten–Alkylidyne Complexes by Zinc Porphyrins in Self-Assembled Dyads

Bimetallic ethynylanthracenyl functionalised carbynes

Mono- and bimetallic anthracenes functionalised by alkynyl and alkylidynyl substituents are obtained via sequential cross-coupling reactions of the 9-bromoanthracenyl carbyne [W{CC(C₆H₄)₂CBr}(CO)₂(Tp*)].

Symmetric and non-symmetric anthracen-diyl bis(alkylidynes)

Three examples of 9-bromo-10-(alkylidynyl)anthracenes, [W{CC(C₆H₄)₂CBr}(CO)₂(L)] (L = hydrotris(dimethylpyrazol-1-yl)borate Tp*, hydrotris(pyrazol-1-yl)borate Tp, hydrotris(2-mercapto-N-methylimidazol-1-yl)borate Tm) were prepared via modified Fischer-Mayr acyl oxide-abstraction protocols. With a sufficiently bulky ancillary ligand (L = Tp*) the aryl bromide is ammenable to cross-coupling reactions that enable more elaborate derivatives to be prepared. These including symmetric bis(alkylidynyl)anthracenes as well as non-palindromic examples bearing disparate metals and/or co-ligands. In contrast, these couplings fail for smaller ligands (L = Tp, Tm) where it was found that Pd⁰ or Pt⁰ were instead able to coordinate across two WC bonds to give trimetallic bow-tie complexes, [W₂M{μ-CC(C₆H₄)₂CBr}₂(CO)₄(L)₂] (M = Pd, Pt; L = Tp, Tm).

Intramolecular photoinduced electron transfer reactions of zinc(II) porphyrin dyads studied with a sub-ns time resolution

We report the dynamics of a intramolecular photoinduced electron transfer reaction of Zn(II)-porphyrin dyads that have a 2,2[Formula: see text]-bipyridine moiety at the periphery in the presence of Cu[Formula: see text] in methanol studied using laser flash photolysis with a sub-nanosecond time resolution. The photoinduced electron transfer reactions were observed from the excited [Formula: see text] and [Formula: see text] states of the Zn(II)-porphyrin to the Cu(II)-2,2[Formula: see text]-bipyridine moiety, and the structural dependence of the reactivity were discussed in terms of the distance between the electron donating and accepting centers.

Carbyne decorated porphyrins

Porphyrins peripherally decorated with four transition-metal carbynes substituents are obtained in one step via a Pd⁰/Au^I transmetallation shuttle beginning with a stannyl carbyne.

Synthesis of pyridyl carbyne complexes and their conversion to N-heterocyclic vinylidenes

A new synthetic approach to hetero-aryl substituted carbyne complexes has allowed the synthesis of pyridyl functionalised carbynes and bis(carbynes), alkylation of which affords the first N-heterocyclic vinylidene complexes.

Triplet energy vs. electron transfers in porphyrin- and tetrabenzoporphyrin-carboxylates/Pd3(dppm)3(CO)2+ cluster assemblies; a question of negative charge

The simple replacement of the methyl groups by carboxylates changes the dominant quenching mechanism in dye⋯[Pd32+]_x assemblies from energy to electron transfer.

Chromium(III) Bis-Arylterpyridyl Complexes with Enhanced Visible Absorption via Incorporation of Intraligand Charge-Transfer Transitions

A series of chromium(III) bis-arylterpyridyl complexes containing intraligand charge-transfer (ILCT) excited states were prepared and characterized. These complexes show significant absorption in the visible region due to the ILCT bands. The ILCT bands are tunable across the UV and visible spectrum via incorporation of electron-withdrawing and electron-donating groups on the aryl ring. The absorption of Cr(4'-(4-methoxyphenyl)-2,2':6',2″-terpyridine)₂³⁺ (4) in particular is much stronger in the visible region (ε = 11 900 M^-1 cm^-1 at 450 nm and ε = 5090 M^-1 cm^-1 at 500 nm) than that of the parent complex Cr(tpy)₂³⁺ (tpy = 2,2':6',2″-terpyridine; ε = 2160 M^-1 cm^-1 at 450 nm, and ε = 170 M^-1 cm^-1 at 500 nm). Emission experiments on this series reveal Cr(III)-based phosphorescence with lifetimes from 140 to 600 ns upon excitation into the ILCT bands, which indicates funneling of the excitation energy from ligand-localized excited states to Cr(III)-based excited states. Cyclic voltammograms exhibit at least three reversible ligand-based reductions. The first reduction shows shifts of up to -160 mV compared to Cr(tpy)₂³⁺. The excited-state reduction potential of these complexes ranges from +0.95 to +1.04 V vs the ferrocene/ferrocenium couple, making them potent photooxidants.

Structure dependence of intramolecular electron transfer reactions of simple dyads of a zinc(ii) porphyrin complex bearing a peripheral bipyridine moiety

Photoinduced intramolecular electron transfer and charge recombination reactions were investigated using various Zn(ii)-porphyrin dyads having a 2,2′-bipyridine moiety.

Photophysics of tungsten–benzylidyne complexes derived from s-indacene: synthesis, characterization and DFT studies

The photophysics of the mono- and homobimetallic complexes of tungsten benzylidyne has been examined by using absorption and emission. Theoretical calculations were carried out to gain further understanding of these novel molecular systems.