Extending the original work on the development of a magnetic avalanche detector using Mn_12-ac single-molecule magnet (SMM), we report the results on a significantly lower threshold magnetic avalanche detector using Fe_8 SMM. Fe_8 has an order of magnitude smaller relaxation time that is expected to produce at least 3 orders of magnitude lower avalanche threshold compared to Mn_12-ac. We confirm this experimentally through the detection of gamma particles with energy at least two orders of magnitude lower than the original Mn_12-ac detection demonstrated using alpha particles, limited by the experimentally available radiation source. The true threshold of avalanche may be significantly lower and will be explored with lower energy x-rays and potentially infrared photons.

The detection of a single quantum of energy with high efficiency and a low false positive rate is of considerable scientific interest, from serving as single quantum sensors of optical and infra-red photons to enabling the direct detection of low-mass dark matter. We confirm our initial experimental demonstration of magnetic avalanches induced by scattering of quanta in single-molecule magnet (SMM) crystals made of Mn_12-acetate, establishing the use of SMMs as particle detectors for the first time. Although the current setup has an energy threshold in the MeV regime, our results motivate the exploration of a wide variety of SMMs whose properties could allow for detection of sub-eV energy depositions.

UV irradiation of yellow CH2Cl2 solutions of trans-Fe(CO)3(P((CH2)10)3P) (2a) and PMe3 (10 equiv) gives, in addition to the previously reported dibridgehead diphosphine P((CH2)10)3P (46%), a green paramagnetic complex that crystallography shows to be the trigonal-bipyramidal iron(I) radical trans-[Fe(CO)2(Cl)(P((CH2)10)3P)]• (1a•; 31% after workup). This is a rare example of an isolable species of the formula [Fe(CO)4-n(L)n(X)]• (n = 0-3, L = two-electron-donor ligand; X = one-electron-donor ligand). Analogous precursors with longer P(CH2)nP segments (n = 12, 14, 16, 18) give only the demetalated diphosphines, and a rationale is proposed. The magnetic susceptibility of 1a•, assayed by Evans' method and SQUID measurements, indicates a spin (S) of 1/2. Cyclic voltammetry shows that 1a• undergoes a partially reversible one-electron oxidation, but no facile reduction. The UV-visible, EPR, and 57Fe Mössbauer spectra are analyzed in detail. Complex 2a is similarly studied, and, despite the extra valence electron, exhibits a comparable oxidation potential (ΔE1/2 ≤ 0.04 V). The crystal structure shows a cage conformation, solvation level, disorder motif, and unit cell parameters essentially identical to those of 1a•. DFT calculations provide much insight regarding the structural, redox, and spectroscopic properties.

The world's oceans capture large amounts of atmospheric carbon dioxide (CO2). Consequently, sustainable and scalable carbon removal from seawater could mitigate atmospheric CO2 when coupled with subsequent sequestration. The pH-dependent speciation of CO2 in aqueous media (CO2(aq), HCO3-(aq), and CO32-(aq)) and the low solubility of CO2(aq) have previously motivated the utilization of pH swings to remove dissolved inorganic carbon (DIC) from aqueous and organic solutions. We show for the first time that light-driven DIC removal from seawater can be achieved in a two-compartment flow reactor utilizing metastable photoacids (PAs) to trigger pH swings across a membrane. Whereas some PAs have been previously reported to facilitate CO2(g) removal if dissolved and irradiated in bicarbonate solutions, our current work validates the feasibility of sustainable carbon removal from seawater without requiring "direct contact" between seawater and PAs. Furthermore, our findings support recent mechanistic investigations of the formation of CO2(g) from DIC by merocyanine-derived PAs.

The first example of a homoleptic f-block borolide sandwich complex is presented and shown to be a high-performance single-molecule magnet (SMM). The bis(borolide) complex [K(2.2.2)][[1-(piperidino)-2,3,4,5-tetraphenylborolyl]2Dy] (1) features an unusual example of an anionic Ln3+ metallocene that supports short metal-ligand bonds and a high degree of linearity around the central Dy3+ ion, resulting in comparatively large barriers to magnetization reversal (Ueff = 1600 cm-1 for the most linear orientation) and, importantly, a high blocking temperature (TB, defined as T(τ100s)) of 66 K. These metrics put complex 1 among the very best performing SMMs reported to date and highlight the potential of dianionic borolide ligands to increase ligand field axiality, compared to monoanionic cyclic ligands, to ultimately maximize magnetic anisotropy in f-block-based SMMs.

Borolides (BC42-) can be considered as dianionic heterocyclic analogues of monoanionic cyclopentadienides. Although both are formally six-π-electron donors, we herein demonstrate that the electronic structure of their corresponding transition metal complexes differs significantly, leading to altered properties. Specifically, the 18-electron sandwich complex Ni(iPr2NBC4Ph2)2 (1) features an ∼90° angle between the Ni-B-N planes and is best described as a combination of three limiting resonance structures with the major contribution stemming from a formally Ni2+ species bound to two monoanionic radical (BC4•-) ligands. Compound 1 displays two sequential one-electron oxidation events over a small potential range of <0.2 V, which strikingly contrasts the large potential separations between redox partners in the family of metallocenes, and the potential reasons for this unusual observation are discussed.

Energetic hot electrons generated in Mn-doped quantum dots (QDs) via exciton-to-hot-electron upconversion possess long-range transfer capability. The long-range hot electron transfer allowed for superior efficiency in various photocatalytic reduction reactions compared to conventional QDs, which solely rely on the transfer of band edge electrons. Here we show that the synergistic action of the interfacial hole transfer to the initial reactant and subsequent long-range hot electron transfer to an intermediate species enables highly efficient redox-neutral photocatalytic reactions, thereby extending the benefits of Mn-doped QDs beyond reduction reactions. The photocatalytic conversion of formate (HCOO-) to carbon monoxide (CO), which is an important route to obtain a key component of syngas from an abundant source, is an exemplary redox-neutral reaction that exhibits a drastic enhancement of catalytic efficiency by Mn-doped QDs. Mn-doped QDs increased the formate to CO conversion rate by 2 orders of magnitude compared to conventional QDs with high selectivity. Spectroscopic study of charge transfer processes and the computational study of reaction intermediates revealed the critical role of long-range hot electron transfer to an intermediate species lacking binding affinity to the QD surface for efficient CO production. Specifically, we find that the formate radical (HCOO)•, formed after the initial hole transfer from the QD to HCOO-, undergoes isomerization to the (HOCO)• radical that subsequently is reduced to yield CO and OH-. Long-range hot electron transfer is particularly effective for reducing the nonbinding (HOCO)• radical, resulting in the large enhancement of CO production by overcoming the limitation of interfacial electron transfer.

Lanthanide-transition metal complexes continue to be of interest, not only because of their synthetic challenge but also of their promising magnetic properties. Computational work examining the chemical bonding between lanthanides and transition metals in PyCp(2)Ln-TMCp(CO)(2) (DyPyCp22- = [2,6-(CH2C5H3)(2)C5H3N](2-)) reveals strong Ln-TM dative bonds. Gas-phase optimized geometries are in good agreement with experimental structures at the density functional theory (DFT) level with large-core pseudopotentials. From La to Lu, there is a small increase in the bond dissociation energy, as well as a decrease in Ln-Fe bond lengths. Energy decomposition analyses attribute this trend to an increase in the electrostatic contribution from the decreasing bond length and a modest increase in the orbital contribution. The natural bond orbital analysis clearly indicates that 3d(6) "lone pairs" in the [FeCp(CO)(2)](-) fragment act as a Lewis bases donating nearly 0.5 electron to Ln virtual orbitals of mainly d character. The interfragment bonding was also quantified by the quantum theory of atoms in molecules, which indicates that the Ln-Fe bond is more covalent than the Ca-Fe bond in the hypothetical CpCa-FeCp(CO)(2) but less covalent than the Zn-Fe bond in the hypothetical CpZn-FeCp(CO)(2). Further comparisons suggest that to the [PyCp(2)Ln](+) cation the [FeCp(CO)(2)](-) anion appears much like a halide. Overall, these Ln-TM dative bonds appear to have strong electrostatic contributions as well as significant orbital mixing and dispersion contributions

Lanthanide ferrocenophanes are an intriguing class of organometallic complexes that feature rare six-coordinate trigonal prismatic coordination environments of 4f elements with close intramolecular proximity to iron ions.

The detection of a single quantum of energy with high efficiency and low false positive rate is of considerable scientific interest, from serving as single quantum sensors of optical and infra-red photons to enabling the direct detection of low-mass dark matter. We report the first experimental demonstration of magnetic avalanches induced by scattering of quanta in single-molecule magnet (SMM) crystals made of Mn12-acetate, establishing the use of SMMs as particle detectors for the first time. While the current setup has an energy threshold in the MeV regime, our results motivate the exploration of a wide variety of SMMs whose properties could allow for detection of sub-eV energy depositions.

Temperature-dependent metalation of the new hexadentate ligand (tris(5-(pyridin-2-yl)-1H-pyrrol-2-yl)methane; H3TPM) enables the selective synthesis of both mononuclear (i.e. Na(THF)4[Fe(TPM)], kinetic product) and trinuclear (i.e. Fe3(TPM)2, thermodynamic product) complexes. Exposure of Na(THF)4[Fe(TPM)] to FeCl2 or ZnCl2 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 development of noble metal-free catalysts capable of electrochemically converting carbon dioxide (CO 2 ) selectively into value added compounds remains one of the central challenges in sustainable energy science. Here, we present a systematic study of Fe(II) complexes of the functionalized ligands bpy R PY2Me (bpyPY2Me = 6-(1,1-di(pyridin-2-yl)ethyl)-2,2′-bipyridine) in pursuit of water-stable molecular Fe complexes that are selective for the catalytic formation of CO from CO 2 . Taking advantage of the inherently high degree of tunability of this ligand manifold, we followed a bio-inspired approach by installing protic functional groups of varying acidities (–H, –OH, –OMe, –NHEt, and –NEt2) into the ligand framework to systematically modify the second coordination sphere of the Fe center. This family of [(bpy R PY2Me)Fe(II)] complexes was characterized using single-crystal X-ray analysis, 1H NMR spectroscopy, and mass spectrometry. Comparative catalytic evaluation of this set of compounds via voltammetry and electrolysis experiments identified [(bpy NHEt PY2Me)Fe] 2+ in particular as an efficient, iron-based, non-heme CO 2 electro-reduction catalyst that displays significant selectivity for the conversion of CO 2 to CO in acetonitrile solution with 11 M H 2 O. We propose that the NH group acts as a local proton source for cleaving the C–O bond in CO 2 to form CO. Interestingly, the complex with the most acidic functional group in the second coordination sphere, [(bpy OH PY2Me)Fe] 2+ , favors formation of H 2 over CO. Our results correlate the selectivity of water versus carbon dioxide reduction to the acidity of the second coordination sphere functional group and emphasize the continued untapped potential that synthetic molecular chemistry offers in the pursuit of next-generation CO 2 reduction electrocatalysts.

We report the first f-block-ruthenocenophane complexes 1 (Dy) and 2 (Tb) and provide a comparative discussion of their magnetic structure with respect to earlier reported ferrocenophane analogues. While axial elongation of the rare trigonal-prismatic geometry stabilizes the magnetic ground state in the case of Dy 3+ and results in a larger barrier to magnetization reversal ( U ), a decrease in U is observed for the case of Tb 3+ .

We report the first experimental demonstration of magnetic avalanches induced by scattering of quanta in single-molecule magnet (SMM) crystals made of Mn12-acetate, establishing the use of SMMs as particle detectors for the first time. While the current setup has an energy threshold in the MeV regime, our results motivate the exploration of a wide variety of SMMs whose properties could achieve 10 meV thresholds. If developed, such detectors could serve as single quantum sensors of infrared photons with high efficiency and low dark count rate, and enable the direct detection of sub-GeV dark matter.

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.

Nanowires and nanorods of magnetite (Fe3O4) are of interest due to their varied biological applications but most importantly for their use as magnetic resonance imaging contrast agents. One-dimensional (1D) structures of magnetite, however, are more challenging to synthesize because the surface energy favors the formation of isotropic structures. Synthetic protocols can be dichotomous, producing either the 1D structure or the magnetite phase but not both. Here, superparamagnetic Fe3O4 nanorods were prepared in solution by the reduction of iron oxy-hydroxide (β-FeOOH) nanoneedles with hydrazine (N2H4). The amount of hydrazine and the reaction time affected the phase and morphology of the resulting iron oxide nanoparticles. One-dimensional nanostructures of Fe3O4 could be produced consistently from various aspect ratios of β-FeOOH nanoneedles, although the length of the template was not retained. Fe3O4 nanorods were characterized by transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and SQUID magnetometry.