An official website of the United States government
Abstract A known trinuclear structure was used to design the heterobimetallic mixed‐valent, mixed‐ligand molecule [CoII(hfac)3−Na−CoIII(acac)3] (1). This was used as a template structure to develop heterotrimetallic molecules [CoII(hfac)3−Na−FeIII(acac)3] (2) and [NiII(hfac)3−Na−CoIII(acac)3] (3) via isovalent site‐specific substitution at either of the cobalt positions. Diffraction methods, synchrotron resonant diffraction, and multiple‐wavelength anomalous diffraction were applied beyond simple structural investigation to provide an unambiguous assignment of the positions and oxidation states for the periodic table neighbors in the heterometallic assemblies. Molecules of2and3are true heterotrimetallic rather than a statistical mixture of two heterobimetallic counterparts. Trinuclear platform1exhibits flexibility in accommodating a variety of di‐ and trivalent metals, which can be further utilized in the design of molecular precursors for the NaMM′O4functional oxide materials.
more »
« less
Glycerol‐derived solvents containing two or three distinct functional groups enabled by trifluoroethyl glycidyl ether
Abstract Conversion of epichlorohydrin to glycidyl ethers creates versatile precursors that can be transformed into a variety of molecular species with glycerol skeletons, enabling the design of molecules with highly tailored functionalities. The synthesis of 2,2,2‐trifluoroethyl glycidyl ether (TFGE, IUPAC name: 2‐[(2,2,2‐trifluoroethoxy)methyl]oxirane, CAS# 1535‐91‐7) was optimized to provide high yield/selectivity and good “green metrics.” TFGE was then used as a platform molecule in the synthesis of asymmetric glycerol 1,3‐diether‐2‐alcohol derivatives, which were subsequently transformed to 1,2,3‐triethers or 1,3‐diether‐2‐ketones. The density, viscosity, and CO2solubility of each molecule were measured and compared with those of other glycerol‐derived compounds as well as compounds with similar functional groups. Furthermore, quantum chemical calculations were performed to understand the structure–property–performance relationships of these molecules for CO2absorption. Based on the results in this work, we foresee that TFGE (and similar glycidyl ethers) would offer great flexibility in molecular design of green solvents and precursors to more complex compounds.
more »
« less
- PAR ID:
- 10362962
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- AIChE Journal
- Volume:
- 68
- Issue:
- 3
- ISSN:
- 0001-1541
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
The true molecular conformation and the crystal structure of benzo[ e ]dinaphtho[2,3- a ;1′,2′,3′,4′- ghi ]fluoranthene, 7,14-diphenylnaphtho[1,2,3,4- cde ]bisanthene and 7,16-diphenylnaphtho[1,2,3,4- cde ]helianthrene were determined ab initio by 3D electron diffraction. All three molecules are remarkable polycyclic aromatic hydrocarbons. The molecular conformation of two of these compounds could not be determined via classical spectroscopic methods due to the large size of the molecule and the occurrence of multiple and reciprocally connected aromatic rings. The molecular structure of the third molecule was previously considered provisional. These compounds were isolated as by-products in the synthesis of similar products and were at the same time nanocrystalline and available only in very limited amounts. 3D electron diffraction data, taken from submicrometric single crystals, allowed for direct ab initio structure solution and the unbiased determination of the internal molecular conformation. Detailed synthetic routes and spectroscopic analyses are also discussed. Based on many-body perturbation theory simulations, benzo[ e ]dinaphtho[2,3- a ;1′,2′,3′,4′- ghi ]fluoranthene may be a promising candidate for triplet–triplet annihilation and 7,14-diphenylnaphtho[1,2,3,4- cde ]bisanthene may be a promising candidate for intermolecular singlet fission in the solid state.more » « less
-
Abstract A modular platform for facile access to 1,2,3,9‐tetrahydro‐4H‐carbazol‐4‐ones (H4‐carbazolones) and 3,4‐dihydrocyclopenta[b]indol‐1(2H)‐ones (H2‐indolones) is described. The requisite 6‐ and 5‐membered 2‐arylcycloalkane‐1,3‐dione precursors were readily obtained through a Cu‐catalyzed arylation of 1,3‐cyclohexanediones or by a ring expansion of aryl succinoin derivatives. Enolization of one carbonyl group in the diones, conversion to a leaving group, and subsequent azidation gave 2‐aryl‐3‐azidocycloalk‐2‐en‐1‐ones. This two‐step, one‐pot azidation is highly regioselective with unsymmetrically substituted 2‐arylcyclohexane‐1,3‐diones. The regioselectivity, which is important for access to single isomers of 3,3‐disubstituted carbazolones, was analyzed mechanistically and computationally. Finally, a Rh‐catalyzed nitrene/nitrenoid insertion into theorthoC−H bond of the aryl moiety gave the H4‐carbazolones and H2‐indolones. One carbazolone was elaborated to an intermediate reported in the total synthesis ofN‐decarbomethoxychanofruticosinate, (−)‐aspidospermidine, (+)‐kopsihainanine A. With 2‐phenylcycloheptane‐1,3‐dione, prepared from cyclohexanone and benzaldehyde, the azidation reaction was readily accomplished. However, the Rh‐catalyzed reaction unexpectedly led to a labile but characterizable azirine rather than the indole derivative. Computations were performed to understand the differences in reactivities of the 5‐ and 6‐membered 2‐aryl‐3‐azidocycloalk‐2‐en‐1‐ones in comparison to the 7‐membered analogue, and to support the structural assignment of the azirine.more » « less
-
Abstract Regio‐ and stereoselective distal allylic/benzylic C−H functionalization of allyl and benzyl silyl ethers was achieved using rhodium(II) carbenes derived from N‐sulfonyltriazoles and aryldiazoacetates as carbene precursors. The bulky rhodium carbenes led to highly site‐selective functionalization of less activated allylic and benzylic C−H bonds even in the presence of electronically preferred C−H bonds located α to oxygen. The dirhodium catalyst Rh2(S‐NTTL)4is the most effective chiral catalyst for triazole‐derived carbene transformations, whereas Rh2(S‐TPPTTL)4works best for carbenes derived from aryldiazoacetates. The reactions afford a variety of δ‐functionalized allyl silyl ethers with high diastereo‐ and enantioselectivity. The utility of the present method was demonstrated by its application to the synthesis of a 3,4‐disubstitutedl‐proline scaffold.more » « less
-
Design of hetero tri metallic molecules, especially those containing at least two different metals with close atomic numbers, radii, and the same coordination number/environment is a challenging task. This quest is greatly facilitated by having a heterobimetallic parent molecule that features multiple metal sites with only some of those displaying substitutional flexibility. Recently, a unique heterobimetallic complex LiMn 2 (thd) 5 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate) has been introduced as a single-source precursor for the preparation of a popular spinel cathode material, LiMn 2 O 4 . Theoretical calculations convincingly predict that in the above trinuclear molecule only one of the Mn sites is sufficiently flexible to be substituted with another 3d transition metal. Following those predictions, two hetero tri metallic complexes, LiMn 2−x Co x (thd) 5 ( x = 1 ( 1a ) and 0.5 ( 1b )), that represent full and partial substitution, respectively, of Co for Mn in the parent molecule, have been synthesized. X-ray structural elucidation clearly showed that only one transition metal position in the trinuclear molecule contains Co, while the other site remains fully occupied by Mn. A number of techniques have been employed for deciphering the structure and composition of hetero tri metallic compounds. Synchrotron resonant diffraction experiments unambiguously assigned 3d transition metal positions as well as provided a precise “site-specific Mn/Co elemental analysis” in a single crystal, even in an extremely difficult case of severely disordered structure formed by the superposition of two enantiomers. DART mass spectrometry and magnetic measurements clearly confirmed the presence of hetero tri metallic species LiMnCo(thd) 5 rather than a statistical mixture of two hetero bi metallic LiMn 2 (thd) 5 and LiCo 2 (thd) 5 molecules. Heterometallic precursors 1a and 1b were found to exhibit a clean decomposition yielding phase-pure LiMnCoO 4 and LiMn 1.5 Co 0.5 O 4 spinels, respectively, at the relatively low temperature of 400 °C. The latter oxide represents an important “5 V spinel” cathode material for the lithium ion batteries. Transmission electron microscopy confirmed a homogeneous distribution of transition metals in quaternary oxides obtained by pyrolysis of single-source precursors.more » « less
