Saccharified Uranyl Ions: Self-Assembly of UO22+ into Trinuclear Anionic Complexes by the Coordination of Glucosamine-Derived Schiff Bases

The reaction of UO₂(OAc)₂ ⋅ 2H₂O with the biologically inspired ligand 2-salicylidene glucosamine (H₂ L¹ ) results in the formation of the anionic trinuclear uranyl complex [(UO₂)₃(μ₃-O)( L¹ )₃]²⁻ ( 1 ²⁻), which was isolated in good yield as its Cs-salt, [Cs]₂ 1 . Recrystallization of [Cs]₂ 1 in the presence of 18-crown-6 led to formation of a neutral ion pair of type [M(18-crown-6)]₂ 1 , which was also obtained for the alkali metal ions Rb⁺ and K⁺ (M=Cs, Rb, K). The related ligand, 2-(2-hydroxy-1-naphthylidene) glucosamine (H₂ L² ) in a similar procedure with Cs⁺ gave the corresponding complex [Cs(18-crown-6)]₂[(UO₂)₃(μ₃-O)( L² )₃ ([Cs(18-crown-6)]₂ 2 ). From X-ray investigations, the [(UO₂)₃O( Lⁿ )₃]²⁻ anion (n=1, 2) in each complex is a discrete trinuclear uranyl species that coordinates to the alkali metal ion via three uranyl oxygen atoms. The coordination behavior of H₂ L¹ and H₂ L² towards UO₂²⁺ was investigated by NMR, UV/Vis spectroscopy and mass spectrometry, revealing the in situ formation of the 1 ²⁻ and 2 ²⁻dianions in solution.     

[P3Se4]+: A Binary Phosphorus–Selenium Cation

Although a fairly large number of binary group 15/16 element cations have been reported, no example involving phosphorus in combination with a group 16 element has been synthesized and characterized to date. In this contribution is reported the synthesis and structural characterization of the first example of such a cation, namely a nortricyclane‐type [P₃Se₄]⁺. This cation has been independently discovered by three groups through three different synthetic routes, as described herein. The molecular and electronic structure of the [P₃Se₄]⁺ cage and its crystal properties in the solid state have been characterized comprehensively by using X‐ray diffraction, Raman, and nuclear magnetic resonance spectroscopies, as well as quantum chemical calculations.     

Synthesis and Reactivity of Mono‐, Di‐, and,Triiron Selenocarboxylate Complexes

Treatment of the iron selenide (μ‐Se)[CpFe(CO)₂]₂ with one equivalent of 1, 3, 5‐C₆H₃(COCl)₃ gave the organoiron selenocarboxylate complex CpFe(CO)₂SeCO‐3, 5‐C₆H₃(COCl)₂ ( 1 ), which contains two free acid chloride groups. Complex 1 reacted with amines, thiols, and phenols to produce the corresponding amides CpFe(CO)₂SeCO‐3, 5‐C₆H₃(CONR₂)₂ ( 2 ), thioesters CpFe(CO)₂SeCO‐3, 5‐C₆H₃(COSR)₂( 3 ), and aromatic esters CpFe(CO)₂SeCO‐3, 5‐C₆H₃(CO₂Ar)₂ ( 4 ), respectively. Complex 1 was converted into the diacid CpFe(CO)₂SeCO‐3, 5‐C₆H₃(COOH)₂ ( 5 ) or the diamide CpFe(CO)₂SeCO‐3, 5‐C₆H₃(CONH₂)₂ ( 6 ) complexes by reactions with NaOH or NaNH₂, respectively. The bis(seleno)‐1, 3‐(CpFe(CO)₂SeCO)₂‐5‐C₆H₃(COCl) ( 7 ) and tris(seleno)‐carboxylate 1, 3, 5‐(CpFe(CO)₂SeCO)₃C₆H₃ ( 8 ) complexes were also prepared by controlled reaction of 1, 3, 5‐C₆H₃(COCl)₃ with the iron selenide (μ‐Se)[CpFe(CO)₂]₂. Complexes 1 – 8 were characterized by spectroscopic techniques (IR, ¹H‐NMR) and by elemental analysis as well. The X‐ray structures of CpFe(CO)₂SeCO‐3, 5‐C₆H₃(COCl)₂ ( 1 ) and CpFe(CO)₂SeCO‐3, 5‐C₆H₃(COSCH₂Ph)₂ ( 3b ) were determined.     

Functionalization of Pentaphosphorus Cations by Complexation

The chemistry of polyphosphorus cations has rapidly developed in recent years, but their coordination behavior has remained mostly unexplored. Herein, we describe the reactivity of [P₅R₂]⁺ cations with cyclopentadienyl metal complexes. The reaction of [Cp^ArFe(μ‐Br)]₂ (Cp^Ar=C₅(C₆H₄‐4‐Et)₅) with [P₅R₂][GaCl₄] (R=iPr and 2,4,6‐Me₃C₆H₂ (Mes)) afforded bicyclo[1.1.0]pentaphosphanes ( 1‐R , R=iPr and Mes), showing an unsymmetric “butterfly” structure. The same products 1‐R were formed from K[Cp^Ar] and [P₅R₂][GaCl₄]. The cationic complexes [Cp^ArCo(η⁴‐P₅R₂)][GaCl₄] ( 2‐R [GaCl₄], R=iPr and Cy) and [(Cp^ArNi)₂(η^3:3‐P₅R₂)][GaCl₄] ( 3‐R [GaCl₄]) were obtained from [P₅R₂][GaCl₄] and [Cp^ArM(μ‐Br)]₂ (M=Co and Ni) as well as by using low‐valent “Cp^ArM^I” sources. Anion metathesis of 2‐R [GaCl₄] and 3‐R [GaCl₄] was achieved with Na[BArF₂₄]. The P₅ framework of the resulting salts 2‐R [BArF₂₄] can be further functionalized with nucleophiles. Thus reactions with [Et₄N]X (X=CN and Cl) give unprecedented cyano‐ and chloro‐functionalized complexes, while organo‐functionalization was achieved with CyMgCl.     

Numerical Simulation of Turbulent Flow and Heat Transfer in a Three-Dimensional Channel Coupled with Flow Through Porous Structures

This study investigates numerically the turbulent flow and heat transfer characteristics of a T-junction mixing, where a porous media flow is vertically discharged in a 3D fully developed channel flow. The fluid equations for the porous medium are solved in a pore structure level using an Speziale, Sarkar and Gatski turbulence model and validated with open literature data. Overall, two types of porous structures, consisted of square pores, are investigated over a wide range of Reynolds numbers: an in-line and a staggered pore structure arrangement. The flow patterns, including the reattachment length in the channel, the velocity field inside the porous medium as well as the fluctuation velocity at the interface, are found to be strongly affected by the velocity ratio between the transversely interacting flow streams. In addition, the heat transfer examination of the flow domain reveals that the temperature distribution in the porous structure is more uniform for the staggered array. The local heat transfer distributions inside the porous structure are also studied, and the general heat transfer rates are correlated in terms of area-averaged Nusselt number accounting for the effects of Reynolds number, velocity ratio as well as the geometrical arrangement of the porous structures.     

Eigenstate symmetry probed by biexciton transitions in a single quantum dot

The eigenstate symmetry in CdSe/ZnSe single quantum dots (SQDs) has been studied by low-temperature magnetoluminescence spectroscopy. Regarding both, the fine structure splitting and the polarization properties of the biexciton transition, the influence of exchange and Zeeman interaction on the eigenstate symmetry of the final state of recombination, the ground state of the single exciton, is investigated.     

Synthesis,Characterization, and Crystal Structure of 1,3‐Dipentafluorophenyl‐2,2,2,4,4,4‐hexazido‐1,3‐diaza‐2,4‐diphosphetidine

1,3‐Dipentafluorophenyl‐2,2,2,4,4,4‐hexazido‐1,3‐diaza‐2,4‐diphosphetidine ( 1 ) was synthesized by the reaction of [(C₆F₅)NPCl₃]₂ with trimethylsilyl azide in CH₂Cl₂ and characterized by multinuclear NMR and vibrational spectroscopy. The molecular structure of the compound was determined by single‐crystal X‐ray structure analysis. [(C₆F₅)NP(N₃)₃]₂ crystallizes in the monoclinic space group P2₁/n with a = 9.6414(2), b = 7.4170(1) and c = 15.9447(4) Å, β = 94.4374(9)°, with 2 formula units per unit cell. The bond situation in [(C₆F₅)NP(N₃)₃]₂ has been studied on the basis of NBO analysis. The antisymmetric stretching vibration of the azide groups is discussed. The structural diversity of 1 and 1,3‐diphenyl‐2,2,2,4,4,4‐hexazido‐1,3‐diaza‐2,4‐diphosphetidine in solution and in the solid state depending on the aryl substituent at the nitrogen atom is discussed.