Dynamic Phenomena in Self‐Complementary {2}‐Metallocryptates Probed by Solution 133Cs‐NMR. New Insights into Ion Pairing Processes: X‐Ray Structure and Solid‐State NMR Spectra of a Meandering Species

Two self‐complementary {2}‐metallocryptates, differing in methyl and phenyl substituents, respectively, have been studied by X‐ray analysis, and solid‐state and solution NMR. Mixed Mg/Cs metal methyl complex 2 is a linear polymer in the solid state. The two different Cs sites are confirmed by ¹³³Cs‐solid‐state NMR. By contrast, the analog mixed Mg/Cs metal phenyl complex 4 is a meandering polymer as shown by an actual X‐ray analysis. The four non‐equivalent Cs‐sites in 4 are reflected in the solid‐state NMR spectra. Solution ¹³³Cs‐NMR spectra of 4 reveal two independent dynamic processes: a fast exchange of Cs within contact ion‐pairs and solvent‐separated ion‐pairs (CIP, SSIP), and a slower exchange of ‘inside’ endo Cs, surrounded by three ligands, and ‘outside’ exo Cs involved in the CIP/SSIP equilibrium. Complete line‐shape analysis of variable‐temperature ¹³³Cs‐NMR spectra of 4 yield kinetic parameters of =10.8 kcal/mol for the fast SSIP‐CIP exchange and =13.2 kcal/mol for the slower endo/exo exchange of Cs. DOSY‐NMR Measurements confirm the monomeric nature of 4 in solution.     

Synthesis, magnetic properties, and STM spectroscopy of an unprecedented octanuclear chloro-bridged nickel(II) double cubane

Reaction of nickel(II) chloride hexahydrate with N-n-butyldiethanolamine H(2)L (3) in the presence of LiH in anhydrous THF leads to the formation of the unique octanuclear chloro-bridged nickel(II) double cubane [({Ni(II)(4)(μ(3)-OH)Cl(3)(HL)(3)}μ(2)-Cl)(2)] (4) in 57% yield. According to single crystal X-ray structure analysis, complex 4·4CH(2)Cl(2) possesses a [({Ni(4)(μ(3)-OH)(μ(3)-O)(3)(OH)(3)(N)(3)(Cl)(3)}μ(2)-Cl)(2)] core and crystallizes in the monoclinic space group P2(1)/c with a = 18.292(2), b = 19.8972(5), c = 23.295(2) ?, β = 98.408(6)°, V = 8387.3(8) ?(3), and four molecules in the unit cell. The analysis of the SQUID magnetic susceptibility data identified 4 as a weakly coupled dimer (J(1) = 14.5 K, J(2) = -0.6 K) with a ground state of S = 0, resulting from two S = 4 states of each {Ni(4)} subunits. Although complex 4 does not show an ac out-of-phase signal in a zero dc field at temperatures of 1.8 K and higher, low-temperature magnetization measurements revealed that complex 4 is a single-molecule magnet and shows hysteretic magnetization characteristics with typical temperature and sweep-rate dependencies. The eye-catching feature of complex 4 is the presence of two different blocking temperatures (0.9 K around zero field and 1.3 K at higher fields). The origin of this highly unusual behavior can be assigned to the dimer-nature of the interaction between the two S = 4 units. Furthermore STM and current imaging tunnelling spectroscopy (CITS) were performed on aggregates of 4 drop-coated on highly oriented pyrolytic graphite (HOPG) surfaces. CITS measurements show a strong contrast in the area of the nickel centers and a HOMO-LUMO gap of approximately 0.8 V.     

Twist dynamics of 9-(N-carbazolyl)-anthracene: effects of Intramolecular Vibrational Redistribution and non-adiabatic transitions in coupled bright and dark states

The twist dynamics of 9-(N-carbazolyl)-anthracene (C9A) in the electronically excited bright and dark states S ₁ and S _X is investigated theoretically. Effects of Intramolecular Vibrational Redistribution (IVR) as well as the diabatic transition S ₁ → S _X are taken into account. Based on a model hamiltonian and IVR-rates, which have been derived earlier from laser induced fluorescence spectra and life times observed by Monte et al. [1], the Liouville-von Neumann equation is integrated with a dissipative Liouvillian in Lindblad form. The resulting time dependent density matrix yields nearly coherent twist dynamics of this rather large molecule, at least on a timescale of several ps. The corresponding pump-probe spectra are predicted following the approach proposed by Manz et al. [2].     

新型BrФnsted酸性离子液体的合成与表征

制备了五种对水稳定性好、带-SO3H官能团的磺酸类BrФnsted酸离子液体,用核磁共振(NMR)、红外光谱(IR)、电喷雾质谱(ESI-MS)、热重分析(TG)等表征手段对制备的离子液体进行了表征。结果表明,制备的离子液体与预期设计的结构一致,离子液体纯度大于95%;热重分析发现离子液体具有高的热稳定性和较宽的液态范围,其分解温度均高于300℃;五种离子液体均存在四种离子存在形式,H 可以单独以离子形式存在,并不是通常所认为的仅有两种离子存在形式。另外,研究了离子液体在常用溶剂中的溶解性,发现制备的离子液体易溶于水、甲醇,不溶于乙醚、甲苯和乙酸乙酯。     

Host‐Guest Complexes of [TriPip222], the Piperazine Analogue of [2.2.2]: Prediction of Ion Selectivity by Quantum Chemical Calculations VIII[#]

The selectivity of the cryptand [TriPip222], a per‐aza analogue of cryptand [2.2.2], in which each of the linking arms contains a piperazine ring for the endohedral complexation of metal cations of the I, II, and III main groups and group 12 of the periodic table of elements, was predicted on the basis of DFT [B3LYP/LANL2DZp (LANL2DZp = LANL2DZ augmented with polarization functions on non‐hydrogen atoms)] calculated structures and complex‐formation energies. The cavity size of the studied cryptand is similar to that of [bpy.bpy.bpy], [2.bpy.bpy] and [2.phen.phen], such that the complexation of K⁺ > Na⁺ and of Sr²⁺ ≈ Ca²⁺ > Ba²⁺ are most favorable. The essential flexibility for achieving the selectivity of the cryptand is mainly associated with a twist of the CH₂–N_bridgehead ··· N_bridgehead–CH₂ angle and not with the piperazine moiety.     

New7Be(p, γ)8B cross section measurement

The⁷Be(p,γ)⁸B cross section has been re-measured using radioactive targets. The zero-energy astrophysical S-factor is found significantly lower than the previously adopted value.