Inspired by the newly discovered sandwich D5d [Os(η5-B5H10)2] as a carbon-free analog of ferrocene [Fe(η5-C5H5)2] and based on extensive global searches and first-principles theory calculations, we present herein the viable possibility of a staggered sandwich bis(η6-cycloborane)chromium D6d [Cr(η6-B6H12)2] (1) with two equivalent η6-B6H12 ligands isovalent with benzene as the boron analog of the eclipsed bis(η6-benzene)chromium D6h [Cr(η6-C6H6)2] (2). Detailed coordination bonding pattern, energy decomposition, and magnetically induced ring current analyses indicate that D6d 1 matches the 18-electron rule (1S21P61D10) and exhibits similar aromaticity to D6h 2, rendering high stability to the system. The metal–ring coordination bonding in D6d 1 is dominated by effective Cr → (η6-B6H12)2 δ-back-donations which appear to be significantly stronger than the corresponding Cr → (η6-C6H6)2 δ-back-donations in D6h 2, leading to an unusually short ring–ring distance of 2.70 Å and a large HOMO-LUMO gap of 7.06 eV in 1. D6d 1 and D6h 2 can also be used as building blocks to form their sandwich tetramers D2h [Cr4B48H76] (3) and D2h [Cr4C48H28] (4) and sandwich two-dimensional nanosheets [Cr(η6-B6H6)2] (5) and [Cr(η6-C6)2] (6) via partial or complete dehydrogenations, respectively.
The development of less toxic nanoparticles capable of producing and selectively sensing organic pollutants remains a significant challenge in biological and environmental applications. In this study, ZnInS/ZnS quantum dots (QDs) were synthesized via an aqueous-phase doping approach to integrate manganese (Mn) and enhance the singlet oxygen quantum yield (SOQY). The as-synthesized QDs displayed an average particle size of 7.40 nm, prolonged photoluminescence lifetimes, and tunable emission characteristics. Introduction of Mn into the host QDs enhanced the absolute quantum yield by up to twofold at the optimal concentrations, while the increased concentrations resulted in reduced luminescence due to increased non-radiative recombination. The surface chemistry of stabilizing agents further improved the formation of singlet oxygen. Thioglycolic acid (TGA)- and gelatin-capped QDs generated higher SOQY than QDs capped with citrate and TGA. Furthermore, as-synthesized Mn-doped QDs detected different organic pollutants such as trinitrophenol (TNP), dichlorophenol (DCP), naphthalene (NP), phenanthrene (PH), and pyrene (PY). Among these pollutants, TNP showed quenching behavior, while the others showed enhancement behavior. The QDs detected 620 µM of TNP following a linear Stern–Volmer relationship. These results show the potential of water-soluble Mn–ZnInS/ZnS QDs as multifunctional nanoprobes for phototherapy and environmental sensing applications.
This review summarizes the methods for the synthesis of α-phosphonocinnamates and their heterocyclic analogs, which have found important applications in materials chemistry, as convenient building blocks in organic synthesis and in other areas of science and technology. Five complementary disconnections are critically compared: (i) Knoevenagel condensation of phosphonoacetates or phosphonoacetic acid with (hetero)aromatic aldehydes and N-tosylimines under amine, amine/carboxylic acid, or amine/Lewis acid catalysis; (ii) arsine-mediated condensation of 2-bromophosphonoacetates with aldehydes; (iii) Mn(III)- or Ag(I)-mediated radical C–P bond formation on cinnamic esters; (iv) phosphine-catalyzed hydrophosphonylation of arylpropiolates; and (v) Heck coupling of aryldiazonium salts with α-phosphonoacrylates. The factors that govern (E)/(Z) selectivity, the substrate scope (electron-rich versus electron-deficient (hetero)arenes), and the chemoselectivity issues encountered with salicylaldehydes—where acyclic phosphonocinnamates, 3-phosphonocoumarins, and [1,2]benzoxaphosphinines (2-phosphacoumarins) compete—are analyzed in detail. A dedicated section covers the synthesis of coumarin-3-phosphonates, including Knoevenagel-type cyclization, Mn(III), Ag(I), Cu or Pd-catalyzed and electrochemical phosphorylation of preformed coumarins, decarboxylative phosphorylation, and intramolecular cyclization strategies. Conflicting literature reports are reconciled where possible, and the practical strengths and limitations of each protocol are highlighted to guide method selection.
Reaching net-zero emissions requires more than displacing fossil combustion with renewable electricity; several of the largest industrial emitters—cement, steel, chemicals, and aviation—cannot be fully electrified with current technology, and captured carbon dioxide (CO2) itself must find a productive destination rather than remain a permanent liability. Converting CO2 into formic acid (HCOOH) has emerged as one of the more mature answers to that second problem. Formic acid combines a respectable hydrogen content (4.4 wt%), a stable liquid state at ambient conditions, and comparatively benign handling relative to gaseous or cryogenic hydrogen, positioning it as both a chemical feedstock and an energy carrier. This review synthesizes the current state of CO2-to-HCOOH conversion across thermochemical, electrochemical, photocatalytic, and biocatalytic routes; examines formic acid’s performance as a liquid organic hydrogen carrier (LOHC) and direct fuel-cell fuel; and evaluates the technology through a recently published pilot-scale case study of a photocatalytic reactor, branded RK-X, developed by the author’s employer—presented here as a single illustrative example rather than a representative benchmark—to show both the promise and the unresolved energetic and economic questions still facing the field. We conclude that formic acid-based CO2 utilization is technically credible and policy-relevant, but that claims of net energy or carbon benefit must be assessed pathway-by-pathway, powered overwhelmingly by low-cost renewable electricity, and confirmed through independent life-cycle assessment before the technology can be considered a settled pillar of the net-zero toolkit.
The solvent dependence of the optical properties of tris(thenoyltrifluoroacetonate)(1,10-phenanthroline)europium(III) (Eu(TTA)3Phen) solution was studied in chloroform, dichloromethane, toluene, acetonitrile, acetone, N,N-dimethylformamide, dimethyl sulfoxide, and methanol. The optical properties of solid Eu(TTA)3Phen were carefully studied for comparison. The absorption spectra are dominated by ligand-centered bands, with only minor solvent-induced changes in the absorption maxima. Upon excitation into the ligand band, the emission spectra containe the characteristic narrow transition bands of europium(III), indicating efficient ligand-to-metal energy transfer. The photochemical properties of Eu(TTA)3Phen significantly depend on the solvent. Nonpolar and weakly coordinating solvents preserve longer lifetimes and higher solution quantum yields, with maxima in chloroform (14.7%) and toluene (13.7%). In contrast, methanol produces the strongest perturbation, yielding the shortest lifetime (0.364 ms), highest nonradiative rate (1427 s−1), lowest Eu(III) internal quantum yield (48.0%), and lowest photoluminescence quantum yield (4.6%). Analysis of radiative/nonradiative rates and 5D0-level formation quantum yield shows that solvent-dependent luminescence arises from changes in both the Eu3+-radiative transition efficiency and ligand-to-metal sensitization, providing design guidelines for solution-processable Eu3+ emitters.
