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The efficient light-driven fuel production from homogeneous photocatalytic systems is one promising avenue towards an alternative energy economy. However, electron transfer from a conventional photosensitizer to a catalyst is short-range and necessitates spatial proximity between them. Here we show that energetic hot electrons generated by Mn-doped semiconductor quantum dots (QDs) allow for long-range sensitization of Ni(cyclam)-based molecular catalysts, enabling photocatalytic reduction of CO 2 to CO without requiring chemical linkages between the QDs and catalyst molecules. Our results demonstrate the potential of hot electron sensitization in simplifying the design of hybrid catalyst systems while improving photocatalytic activity. 

Lanthanide metallocenophanes are an intriguing class of organometallic complexes that feature rare six-coordinate trigonal prismatic coordination environments of 4f elements with close intramolecular proximity to transition metal ions. Herein, we present a systematic study of the structural and magnetic properties of the ferrocenophanes, [LnFc 3 (THF) 2 Li 2 ] − , of the late trivalent lanthanide ions (Ln = Gd ( 1 ), Ho ( 2 ), Er ( 3 ), Tm ( 4 ), Yb ( 5 ), Lu ( 6 )). One major structural trend within this class of complexes is the increasing diferrocenyl (Fc 2− ) average twist angle with decreasing ionic radius ( r ion ) of the central Ln ion, resulting in the largest average Fc 2− twist angles for the Lu 3+ compound 6 . Such high sensitivity of the twist angle to changes in r ion is unique to the here presented ferrocenophane complexes and likely due to the large trigonal plane separation enforced by the ligand (>3.2 Å). This geometry also allows the non-Kramers ion Ho 3+ to exhibit slow magnetic relaxation in the absence of applied dc fields, rendering compound 2 a rare example of a Ho-based single-molecule magnet (SMM) with barriers to magnetization reversal ( U ) of 110–131 cm −1 . In contrast, compounds featuring Ln ions with prolate electron density ( 3–5 ) don't show slow magnetization dynamics under the same conditions. The observed trends in magnetic properties of 2–5 are supported by state-of-the-art ab initio calculations. Finally, the magneto-structural relationship of the trigonal prismatic Ho-[1]ferrocenophane motif was further investigated by axial ligand (THF in 2 ) exchange to yield [HoFc 3 (THF*) 2 Li 2 ] − ( 2-THF* ) and [HoFc 3 (py) 2 Li 2 ] − ( 2-py ) motifs. We find that larger average Fc 2− twist angles (in 2-THF* and 2-py as compared to in 2 ) result in faster magnetic relaxation times at a given temperature. 

Temperature-dependent metalation of the new hexadentate ligand (tris(5-(pyridin-2-yl)-1 H -pyrrol-2-yl)methane; H 3 TPM) enables the selective synthesis of both mononuclear ( i.e. Na(THF) 4 [Fe(TPM)], kinetic product) and trinuclear ( i.e. Fe 3 (TPM) 2 , thermodynamic product) complexes. Exposure of Na(THF) 4 [Fe(TPM)] to FeCl 2 or ZnCl 2 triggers cluster expansion to generate homo- or heterometallic trinuclear complexes, respectively. The developed approach enables systematic variation of ion content in isostructural metal clusters via programmed assembly. 

The syntheses, structural, and magnetic characterization of three new organometallic Ce complexes stabilized by PyCp 2 2− (PyCp 2 2− = [2,6-(CH 2 C 5 H 3 ) 2 C 5 H 3 N] 2− ) are reported. Complex 1 provides the first example of a crystallographically characterized unsupported Ce–Fe bond in a molecular compound. Results from IR spectroscopy and computational analyses suggest weaker Fe → Ce electron-donation than in a previously reported Dy–Fe bonded species.