The decreased excited state lifetime of Rh III phenPer (reduced by a factor of 8 compared to phenPer), further corroborates charge transfer from the Per moiety towards the Rh center. This is also reflected in the emission quenching upon coordination of phenPer to Rh III (see Fig. ). In comparison to hybrid rylene imide-transition metal complex architectures reported earlier, that show charge recombination of their radical anions 10 or cations 34 on the sub-100 ps timescale, the herein studied [(phenPer •+ )Rh II (Cp*)Cl] + reveals an enhanced CS state lifetime. In contrast, the CS state of the structurally related, dinuclear transition metal complex [(tbbpy)2Ru(tpphz)Rh(Cp*)Cl] 3+ (Ru II -tpphz-Rh III , tpphz: tetrapyrido[3,2-a:2′,3′-c:3′′,2′′-h:2′′′,3′′′-j]phenazine, tbbpy: 4,4′-di-tert-butyl-2,2′-bipyridine) is long-lived (> 2 ns 16 ) compared to the CS state of Rh III phenPer, which can be rationalized by the comparably short charge separation distance. Formation of the catalytically active species and redox catalysis. The formation of a fully charged Rh I species is key to the overall performance of the Rh III -catalysts. To explore the multi-electron photocatalytic mechanism, the fully charged catalyst (Rh I phenPer) was selectively generated via the three following pathways: i) chemical reduction of the Rh III center by a formate-driven thermal reaction 35 (see Fig. ), ii) electrochemical reduction (see Fig. ), and iii) photochemical reduction upon LED-illumination in the presence of triethylamine (TEA) as sacrificial electron donor (see Fig. ). The in situ spectra obtained via those three methods are qualitatively identical (see Fig. ) and indicate the formation of Rh I phenPer. This is revealed in the rise of a characteristic absorption band at 695 nm, which is assigned to Rh I →phen MLCT transitions. To evaluate the capability of Rh I phenPer to drive the hydrogenation of NAD + , 37 the increase in absorbance at 340 nm associated with ππ* transitions of NADH, was monitored in situ. Those studies reveal the successful reduction of NAD + to NADH at a constant turnover frequency (see Fig. , S23 -S27). The chemical reduction, i.e., formate-driven activation of the catalyst serves as a wellunderstood benchmark for evaluation of a catalytically competent Rh(Cp*) sphere. In this setting, a turnover number of circa 30 (75% conversion) is obtained during an overall reaction time of 70 minutes at 40°C which is about three times lower at room temperature (see Fig. and). In addition, Rh III phenPer shows light-driven catalytic activity. Upon 70 minutes of LED illumination at 400 nm (14 mW•cm -2 ) or 470 nm (45 mW•cm -2 ), respectively, an average turnover number of circa 4 (10% conversion) is found at room temperature (see Fig. and S25 -S27). Increasing the temperature to 40°C yields a TON of 4 or 7 upon illumination at 400 or 470 nm for 70 minutes, respectively. The lower turnover compared to the chemical setting can be explained by the necessary coordination of NAD + to the catalytically active [(phenPer)Rh III (Cp*)H] species (Rh III HphenPer) or its tautomerized form, respectively. This species forms rapidly upon protonation of Rh I phenPer, as revealed by the absence of the typical Rh I phenPer absorption at 695 nm under photochemical conditions (see Fig. ).