[Cr(ttpy)2]3+ as a multi-electron reservoir for photoinduced charge accumulation

Abstract

Under visible light irradiation [Cr(ttpy)2]3+ can be reduced twice by a tertiary amine; the photoreduction processes are accelerated in the presence of [Ru(bpy)3]2+ acting as an antenna thanks to an efficient electron transfer reaction from [Ru(bpy)3]2+* to [Cr(ttpy)2]3+.

Luminescence and Light‐Driven Energy and Electron Transfer from an Exceptionally Long‐Lived Excited State of a Non‐Innocent Chromium(III) Complex

“…1.75 eV at room temperature (from the 0‐0 energy of the emission band fit, Figure S15) and the redox potential of the [Cr(tpe) 2 ] 3+/2+ couple, the excited state reduction potential amounts to +0.87 V vs. FcH/FcH + (+1.25 V vs. SCE). This exceeds the potential of commonly employed photoredox catalysts [Ru(bpy) 3 ] 2+ (+0.77 V vs. SCE) and fac ‐Ir(ppy) 3 (+0.31 V vs. SCE; ppy=anion of 2‐phenylpyridine), yet is smaller than that of the strongest chromium(III) derived photooxidants ([Cr(dmcbpy) 3 ] 3+ : +1.84 V vs. SCE; dmcbpy=4,4′‐di(methylcarboxyl)‐2,2′‐bipyridine; [Cr(ttpy) 2 ] 3+ : +1.44 V vs. SCE; ttpy=4′‐( p ‐tolyl)‐2,2′:6,2′′‐terpyridine) . In terms of excited state lifetime, [Cr(tpe) 2 ] 3+ surpasses all these sensitizers by orders of magnitude ( τ ([Ru(bpy) 3 ] 2+ )=1.1 μs; τ ( fac ‐Ir(ppy) 3 )=1.9 μs; τ ([Cr(dmcbpy) 3 ] 3+ )=7.7 μs; τ ([Cr(ttpy) 2 ] 3+ )=0.27 μs) …”

Key Strategy for the Rational Incorporation of Long-Lived NIR Emissive Cr(III) Chromophores into Polymetallic Architectures

“…Alternative inert metallic centers cannot benefit from this strategy, but they are not excluded from their inclusions into designed polymetallic architectures such that the “complex-as-ligand” strategy can be exploited. , In this case, a heteroleptic inert metal complex which holds at least one available free binding unit is preformed and used as a receptor for further complexation reactions. This strategy was shown to be particularly useful and successful for the introduction of inert Ru II chromophores into metallosupramolecular assemblies. − These complexes were found to be appealing because of their easy structure elucidation by NMR, their compatibility with postfunctionalization methods, and their 3 MLCT excited state, the lifetime and energy of which are suitable for water splitting − or charge separation processes. − However, the microsecond range excited state lifetime spanned by costly Ru II is not optimal for the design of technologically adapted energy-converting devices. The much cheaper Cr III N 6 chromophores, which display long near-infrared (NIR) emission lifetimes that can reach the millisecond range in solution at room temperature, might be better suited for collecting and redistributing light-excitation. − Despite those outstanding photophysical properties which led to the first implementation of linear upconversion in a molecular chromium-containing compound, − Cr III N 6 inert complexes have been rarely introduced into designed polymetallic architectures because of (i) their only partial robustness regarding cross-coupling reactions, (ii) the scarce synthetic methods available for the preparation of heteroleptic Cr III complexes, ,− and (iii) the lack of an accessible simple quantitative characterization method in solution since high-resolution NMR spectroscopy is hampered by the long electronic relaxation time of the Cr­( 4 A 2 ) paramagnetic ground state.…”

“…This strategy was shown to be particularly useful and successful for the introduction of inert Ru II chromophores into metallosupramolecular assemblies. [15][16][17][18][19][20][21][22][23][24][25] These complexes were found to be appealing because of their easy structure elucidation by NMR, their compatibility with post-functionalisation methods and their 3 MLCT excited state, the lifetime and energy of which are suitable for water splitting [26][27][28][29] or charge separation processes. [30][31][32][33][34] However, the microsecond range excited state lifetime spanned by costly Ru II is not optimal for the design of technologically-adapted energy converting devices.…”

Manganese(I) Complex with Monodentate Arylisocyanide Ligands Shows Photodissociation Instead of Luminescence

“… 56 − 59 Advances in ligand design, photophysical techniques, and theoretical understanding 60 have made an unexpectedly broad range of transition metals in different oxidation states useable for photophysical or photochemical applications. In particular, luminescent first-row transition metal complexes with V, 61 − 64 Cr, 65 − 73 Mn, 53 , 74 − 76 Fe, 28 , 34 , 42 , 77 − 79 Co, 71 , 80 − 800 Ni, 83 − 86 and Cu 87 − 96 with different types of electronically excited states featuring promising photoreactivity and photoluminescence behavior have been discovered recently. 56 , 57 , 59 , 97 , 98 …”