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  1. Free, publicly-accessible full text available October 12, 2023
  2. Redox-active multimetallic platforms with synthetically addressable and hemilabile active sites are attractive synthetic targets for mimicking the reactivity of enzymatic co-factors toward multielectron transformations. To this end, a family of ternary clusters featuring three edge metal sites anchored on a [Co 6 Se 8 ] multimetallic support via amidophosphine ligands are a promising platform. In this report, we explore how small changes in the stereoelectronic properties of these ligands alter [Co 6 Se 8 ] metalloligand formation, but also substrate binding affinity and strength of the edge/support interaction in two new ternary clusters, M 3 Co 6 Se 8 L 6 (M = Zn, Fe; L (−) = Ph 2 PN (−)i Pr). These clusters are characterized extensively using a range of methods, including single crystal X-ray diffraction, electronic absorption spectroscopy and cyclic voltammetry. Substrate binding studies reveal that Fe 3 Co 6 Se 8 L 6 resists coordination of larger ligands like pyridine or tetrahydrofuran, but binds the smaller ligand CN t Bu. Additionally, investigations into the synthesis of new [Co 6 Se 8 ] metalloligands using two aminophosphines, Ph 2 PN(H) i Pr (L H ) and i Pr 2 PN(H) i Pr, led to the synthesis andmore »characterization of Co 6 Se 8 L H 6 , as well as the smaller clusters Co 4 Se 2 (CO) 6 L H 4 , Co 3 Se(μ 2 -PPh 2 )(CO) 4 L H 3 , and [Co(CO) 3 ( i Pr 2 PN(H) i Pr)] 2 . Cumulatively, this study expands our understanding on the effect of the stereoelectronic properties of aminophosphine ligands in the synthesis of cobalt chalcogenide clusters, and, importantly on modulating the push–pull dynamic between the [Co 6 Se 8 ] support, the edge metals and incoming coordinating ligands in ternary M 3 Co 6 Se 8 L 6 clusters.« less
  3. The addition of tert -butyl hydroperoxide ( t BuOOH) to two structurally related Mn II complexes containing N,N -bis(6-methyl-2-pyridylmethyl)ethane-1,2-diamine (6-Me-DPEN) and N,N -bis(6-methyl-2-pyridylmethyl)propane-1,2-diamine (6-Me-DPPN) results in the formation of high-valent bis-oxo complexes, namely di-μ-oxido-bis{[ N , N -bis(6-methyl-2-pyridylmethyl)ethane-1,2-diamine]manganese(II)}( Mn — Mn ) bis(tetraphenylborate) dihydrate, [Mn(C 16 H 22 N 4 ) 2 O 2 ](C 24 H 20 B) 2 ·2H 2 O or {[Mn IV (N 4 (6-Me-DPEN))] 2 ( μ -O) 2 }(2BPh 4 )(2H 2 O) ( 1 ) and di-μ-oxido-bis{[ N , N -bis(6-methyl-2-pyridylmethyl)propane-1,3-diamine]manganese(II)}( Mn — Mn ) bis(tetraphenylborate) diethyl ether disolvate, [Mn(C 17 H 24 N 4 ) 2 O 2 ](C 24 H 20 B) 2 ·2C 4 H 10 O or {[Mn IV (N 4 (6-MeDPPN))] 2 ( μ -O) 2 }(2BPh 4 )(2Et 2 O) ( 2 ). Complexes 1 and 2 both contain the `diamond core' motif found previously in a number of iron, copper, and manganese high-valent bis-oxo compounds. The flexibility in the propyl linker in the ligand scaffold of 2 , as compared to that of the ethyl linker in 1 , results in more elongated Mn—N bonds, as one would expect. The Mn—Mn distances and Mn—O bond lengthsmore »support an Mn IV oxidation state assignment for the Mn ions in both 1 and 2 . The angles around the Mn centers are consistent with the local pseudo-octahedral geometry.« less
  4. Tuning the properties of atomic crystals in the two-dimensional (2D) limit is synthetically challenging, but critical to unlock their potential in fundamental research and nanotechnology alike. 2D crystals assembled using superatomic blocks could provide a route to encrypt desirable functionality, yet strategies to link the inorganic blocks together in predetermined dimensionality or symmetry are scarce. Here, we describe the synthesis of anisotropic van der Waals crystalline frameworks using the designer superatomic nanocluster Co 3 (py) 3 Co 6 Se 8 L 6 (py = pyridine, L = Ph 2 PN(Tol)), and ditopic linkers. Post-synthetically, the 3D crystals can be mechanically exfoliated into ultrathin flakes (8 to 60 nm), or intercalated with the redox-active guest tetracyanoethylene in a single-crystal-to-single-crystal transformation. Extensive characterization, including by single crystal X-ray diffraction, reveals how intrinsic features of the nanocluster, such as its structure, chirality, redox-activity and magnetic profile, predetermine key properties of the emerging 2D structures. Within the nanosheets, the strict and unusual stereoselectivity of the nanocluster's Co edges for the low symmetry (α,α,β) isomer gives rise to in-plane structural anisotropy, while the helically chiral nanoclusters self-organize into alternating Δ- and Λ-homochiral rows. The nanocluster's high-spin Co edges, and its rich redox profile make themore »nanosheets both magnetically and electrochemically active, as revealed by solid state magnetic and cyclic voltammetry studies. The length and flexibility of the ditopic linker was varied, and found to have a secondary effect on the structure and stacking of the nanosheets within the 3D crystals. With these results we introduce a deterministic and versatile synthetic entry to programmable functionality and symmetry in 2D superatomic crystals.« less
  5. A green and scalable method to synthesize organic luminophores with minimal aggregation caused quenching (ACQ) is reported where direct arylation is used to attach alkylated theobromine moieties onto luminophores. The resulting compounds demonstrated high photoluminescence quantum yields (PLQYs) in solution and as aggregates. The minimized ACQ can be ascribed to the large dihedral angles that theobromine moieties introduce into these molecules, preventing π–π interactions between the luminophores. Furthermore, the large dihedral angles promote the formation of hybridized local and charge-transfer states in these molecules. Finally, amplified spontaneous emission measurements were performed to explore their potential in lasers.
  6. In order to shed light on metal-dependent mechanisms for O–O bond cleavage, and its microscopic reverse, we compare herein the electronic and geometric structures of O2-derived binuclear Co(III)– and Mn(III)–peroxo compounds. Binuclear metal peroxo complexes are proposed to form as intermediates during Mn-promoted photosynthetic H2O oxidation, as well as a Co-containing artificial leaf inspired by nature’s photosynthetic H2O oxidation catalyst. Crystallographic characterization of an extremely activated peroxo is made possible by working with substitution-inert, low-spin Co(III). Density functional theory (DFT) calculations show that the frontier orbitals of the Co(III)–peroxo compound differ noticeably from the analogous Mn(III)–peroxo compound. The highest occupied molecular orbital (HOMO) associated with the Co(III)–peroxo is more localized on the peroxo in an antibonding π*(O–O) orbital, whereas the HOMO of the structurally analogous Mn(III)–peroxo is delocalized over both the metal d-orbitals and peroxo π*(O–O) orbital. With low-spin d6 Co(III), filled t2g orbitals prevent π-back-donation from the doubly occupied antibonding π*(O–O) orbital onto the metal ion. This is not the case with high-spin d4 Mn(III), since these orbitals are half-filled. This weakens the peroxo O–O bond of the former relative to the latter.
  7. Stoichiometric reduction reactions of two metal–organic frameworks (MOFs) by the solution reagents (M = Cr, Co) are described. The two MOFs contain clusters with Ti 8 O 8 rings: Ti 8 O 8 (OH) 4 (bdc) 6 ; bdc = terephthalate (MIL-125) and Ti 8 O 8 (OH) 4 (bdc-NH 2 ) 6 ; bdc-NH 2 = 2-aminoterephthalate (NH 2 -MIL-125). The stoichiometry of the redox reactions was probed using solution NMR methods. The extent of reduction is greatly enhanced by the presence of Na + , which is incorporated into the bulk of the material. The roughly 1 : 1 stoichiometry of electrons and cations indicates that the storage of e − in the MOF is tightly coupled to a cation within the architecture, for charge balance.