Since the initial report by Lehn et al. in 1979, ruthenium tris(bipyridine) ([Ru(bpy) 3 ] 2+ ) and its numerous derivatives were applied as photosensitizers (PSs) in a large panel of photocatalytic conditions while the bis(terpyridine) analogues were disregarded because of their low quantum yields and short excited-state lifetimes. In this study, we prepared a new terpyridine ligand, 4′-(4-bromophenyl)-4,4‴:4″,4‴′-dipyridinyl-2,2′:6′,2″-terpyridine (Bipytpy) and used it to prepare the heteroleptic complex [Ru(Tolyltpy)(Bipytpy)](PF 6 ) 2 (1; Tolyltpy = 4′tolyl-2,2′:6′,2′-terpyridine). Complex 1 exhibits enhanced photophysical properties with a higher quantum yield (7.4 × 10 -4 ) and a longer excited-state lifetime (3.8 ns) compared to those of [Ru(Tolyltpy) 2 ](PF 6 ) 2 (3 × 10 -5 and 0.74 ns, respectively). These enhanced photophysical characteristics and the potential for PS-catalyst interaction through the peripheral pyridines led us to apply the complex for visible-light-driven hydrogen evolution.The photocatalytic system based on 1 as the PS, triethanolamine as a sacrificial donor, and cobaloxime as a catalyst exhibits sustained activity over more than 10 days under blue-light irradiation (light-emitting diode centered at 450 nm). A maximum turnover number of 764 was obtained after 12 days.

The structure−properties relationship in a series of carbonyl rhenium(I) complexes based on substituted terpyridine ligands of general formula [Re(κ x N-Rtpy)(CO) y L] n+ is explored by both experimental and theoretical methods. In these compounds, the terpyridine ligands adopt both bidentate (κ 2 N) and terdentate (κ 3 N) coordination modes associated with three or two carbonyls, respectively. Conversion from the κ 2 N to the κ 3 N coordination mode leads to large changes in the absorption spectra and oxidation potentials due to destabilization of the HOMO level of each complex. The absorption profiles of the κ 3 N complexes cover the whole visible spectra with lower maxima around 700 nm, tailing out to 800 nm, while no emission is observed with Br − as the axial ligand L. When the axial ligand is modified from the native halide to pyridine or triphenylphosphine, the lowest absorption band is blue-shifted by 60 and 90 nm, respectively. These cationic complexes are near-infrared emitters with emission maxima between 840 and 950 nm for the pyridine compounds and 780−800 nm for the triphenylphosphine compounds.

The synthesis of a Ir(III)-Co(III) dyad with vectorial electron transfer afforded a novel supramolecular system that photocatalytically produces hydrogen in a range extending from the blue region of the spectrum to the red region with higher turnover number and frequency compared to other bimetallic dyads.

A new class of cationic iridium(III) complexes of the form [(C(∧)N)2Ir(N(∧)N)][PF6] is reported, where C(∧)N = cyclometallating 2-phenylpyridinato, ppy, or 2-(2,4-difluorophenyl)-5'-methylpyridinato, dFMeppy, and N(∧)N = guanidyl-pyridine, gpy, or -pyrazine, gpz, as the ancillary ligand. A large blue-shift in the emission coupled with a 7-to-9 fold enhancement in photoluminescence quantum yield and microsecond emission lifetimes were observed for the complexes containing the partially saturated gpy ligand as compared to the benchmark complex [(ppy)2Ir(bpy)][PF6], C1, where bpy is 2,2'-bipyridine.

We report several new dyads constituted of cationic iridium(iii) photosensitizers and cobalt(iii) catalyst connected via free pendant pyridine on the photosensitizers.

The photocatalytic reduction of water to form hydrogen gas (H 2 ) is a promising approach to collect, convert, and store solar energy. Typically, ruthenium tris(bipyridine) and its many derivatives are used as photosensitizers (PSs) in a variety of photocatalytic conditions. The bis(terpyridine) analogues, however, have only recently gained attention for this application because of their poor photophysical properties. Yet, by the introduction of electron-donating or -withdrawing groups on the terpyridine ligands, the photophysical and electrochemical properties can be considerably improved. In this study, we report a series of nonsymmetric 2,6-di(pyridin-2yl)pyrimidine ligands with peripheral pyridine substituents in different positions and their corresponding ruthenium(II) complexes. The presence of the pyrimidine ring stabilizes the lowest unoccupied molecular orbital, leading to a red-shifted emission and prolonged excited-state lifetimes as well as higher luminescence quantum yields compared to analogous terpyridine complexes. Furthermore, all complexes are easier to reduce than the previously reported bis(terpyridine) complexes used as PSs. Interestingly, the pyridine substituent in the 4-pyrimidine position has a greater impact on both the photophysical and electrochemical properties. This correlation between the substitution pattern and properties of the complexes is further investigated by using time-dependent density functional theory. In hydrogen evolution experiments under blue-and red-light irradiation, all investigated complexes exhibit much higher activity compared to the previously reported ruthenium(II) bis(terpyridine) complexes, but none of the complexes are as stable as the literature compounds, presumably because of an additional decomposition pathway of the reduced PS competing with electron transfer from the reduced PS to the catalyst.

A series of new extended planar aromatic ligands based on an acridine core (dpac = dipyrido[3,2-a:2′,3′-c]acridine; dpacF 2 = 7,8-difluorodipyrido[3,2-a:2′,3′-c]acridine; dpacF 4 = 6,7,8,9-tetrafluorodipyrido[3,2-a:2′,3′-c]acridine) and their respective Ru II complexes were synthesized and extensively studied. The photophysical and theoretical studies revealed that Ru-DPAC and Ru-DPACF 2 allow emission from a 3 MLCT phen/dpac excited state at 597 and 604 nm, respectively, whereas the lowest excited state for Ru-DPACF 4 shifts from a [a] 3656 EtOAc (25 mL) was added, followed by a solution of NaOH 2 M until effervescence stops, and MilliQ water (40 mL). The organic phase was separated and the aqueous phase was extracted with Et 2 O (3 × 30 mL). The combined organic phases were dried with MgSO 4 , evaporated, and dried under vacuum. The desired compound was obtained as a beige solid, yield 93 %. 1 H NMR (300 MHz, CDCl 3 ): δ = 7.15 (ddd, J c-d = 8.0, J c-b = 8.0, J c-a = 1.6 Hz, 1 H, H c ), 7.07 (dd, J a-b = 7.6, J a-c = 1.6 Hz, 1 H, H a ), 6.70-6.75 (m, 2 H, H b and H d ), 4.70 (s, 2 H, CH 2 ), 3.19 (br., 2 H, NH 2 ) ppm. dpac (4): 5-Amino-1,10-phenanthroline (183.0 mg, 0.938 mmol) and 2-aminobenzyl alcohol (115.6 mg, 0.938 mmol) were suspended in 6 N HCl (3.0 mL). The reaction mixture was stirred at reflux (65°C) for 20 h and, after cooling to room temperature, the reaction was quenched by addition of NH 3 ·H 2 O until reaching pH 9. The orange precipitate was filtered and purified by using a neutral alumina column for chromatography (eluent: acetone/methanol gradient, from 100:0 to 90:10), yielding the targeted compound as a dark-orange solid, yield 93 %. 1 H NMR (500 MHz, CD 3 OD): δ = 9.77 (dd, J c-b = 8.3, J c-a = 1.8 Hz, 1 H, H c ), 9.68 (s, 1 H, H d ), 9.30 (dd, J i-j = 8.3, J i-k = 1.5 Hz, 1 H, H i ), 9.14 (dd, J a-b = 4.5, J a-c = 1.8 Hz, 1 H, H a ), 9.08 (dd, J k-j = 4.5, J k-i = 1.6 Hz, 1 H, H k ), 8.34 (d, J e-f = 8.7 Hz, 1 H, H e ), 8.26Hz, 2 H, H b and H j ), 7.76 (t, J g-h = 7.2 Hz, 1 H, H g ) ppm. MS (APCI, +c): calcd. 282.10 for C 19 H 12 N 3 , found 282.27 [M + H + ].(2-Amino-4,5-difluorophenyl)methanol: A solution of LiAlH 4 in dry Et 2 O (78.5 mg in 2.0 mL) was added dropwise to a solution of 4,5-difluoroanthranilic acid (200.0 mg, 1.155 mmol) in dry Et 2 O (8.0 mL). The mixture was then stirred at reflux (35°C) for 1 h 15 min. After cooling to room temperature, EtOAc (10 mL) was added, followed by a solution of NaOH (2 M) until effervescence stopped, and MilliQ water (15 mL). The organic phase was separated and the aqueous phase was extracted with Et 2 O (3 × 10 mL). The combined organic phases were dried with MgSO 4 , evaporated, and dried under vacuum. The desired compound was obtained as a flaky yellowish-brownish solid, yield 91 %. 1 H NMR (300 MHz, CDCl 3 ): δ = 6.92 (dd, J a-b = 10.5, J a-c = 8.6 Hz, 1 H, H a ), 6.50 (dd, J d-c = 11.8, J d-b = 6.8 Hz, 1 H, H d ), 4.61 (s, 2 H, CH 2 ), 4.12 (br., 2 H, NH 2 ) ppm. dpacF 2 (5): 5-Amino-1,10-phenanthroline (50.0 mg, 0.256 mmol) and (2-amino...

Three new ruthenium bis-terpyridine complexes bearing both an internal electron donor and peripheral coordination site(s) are used as photosensitisers in H2 photo-evolution under blue and green light with sustained activity for at least two days.