No abstract

No abstract

Taking advantage of the steric hindrance and charge-driving effects, four air-stable pentagonal bipyramidal mononuclear Dy compounds were hydrothermally synthesized. With a tetradentate ligand, N,N'-bis(2-methylenepyridinyl)ethylenediamine (Bpen), invariably coordinates to Dy in an equatorial plan, 1-3 achieve an orderly transformation of the ligand field by sequentially replacing the remaining sites of the Dy ion. Compound 4 possesses the same coordination atoms but a different peripheral coordination sphere with 3. Magnetic characterizations display that the compounds are field-induced single-ion magnets (SIM) with actually low barriers, even though 2 has both the same atoms and a similar geometry of the first sphere compared with [Dy(bbpen)Cl] (2', H bbpen=N,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-methylpyridyl)ethylenediamin), a high-performance SIM previously reported. Detailed ab initio calculations have been employed to further elucidate the electronic and magnetic structure of the low-lying energy levels of compounds 1-4 and 2'. The theoretical results indicate there is an apparent difference in the electronic structure for these compounds. The analysis on the electrostatic potential further demonstrates that although the pentagonal bipyramidal D is one of the ideal configurations expected, the electron density of the donor atoms from the different hybridizations and other functional groups, outside the first sphere, should also be considered in the rational design of promising molecular magnets.

In this work, a large excess of electrostatic repulsion, arising from the axial ligands, over that from the equatorial ligands is taken as the design strategy for high performance pentagonal bipyramidal (PBP) DyIII single-ion magnets (SIMs).

Reaction of Co(II) with the nitrogen-rich ligand N,N-bis(1H-tetrazole-5-yl)-amine (H2bta) leads to a mixed-valence, 3D, porous, metal-organic framework (MOF)-based, energetic material with the nitrogen content of 51.78%, [Co9(bta)10(Hbta)2(H2O)10]n⋅(22 H2O)n (1). Compound 1 was thermohydrated to produce a new, stable, energetic material with the nitrogen content of 59.85% and heat of denotation of 4.537 kcal cm(-3), [Co9(bta)10(Hbta)2(H2O)10]n (2). Sensitivity tests show that 2 is more sensitivity to external stimuli than 1, reflecting guest-dependent energy and sensitivity of 3D, MOF-based, energetic materials. Less-sensitive 1 can be regarded as a more safe form for storage and transformation to sensitive 2.

A reticular 3D heterometallic metal-organic framework (MOF), [Cu4Na(Mtta)5(CH3CN)]n () (N% = 40.08%), has been synthesized, using a 5-methyl tetrazole (Mtta) ligand formed from acetonitrile and azide, through in situ synthesis and structurally characterized by X-ray single crystal diffraction. The fluorescence spectra demonstrate that undergoes an interesting structural transformation in aqueous solution, yielding the compound [Cu4Na(Mtta)5H2O]n () as confirmed by (1)H NMR, IR and PXRD. Thermoanalysis showed that possesses excellent thermostability up to 335 °C. The calculated detonation properties and the sensitivity test illustrate that compound could be used as a potential explosive. In addition, the non-isothermal kinetics for were studied using the Kissinger and Ozawa-Doyle methods. The enthalpy of formation was obtained from the determination of the constant-volume combustion energy.

Utilization of metal-organic frameworks (MOFs) as electrodes for energy storage/conversion is challenging because of the low chemical stability and poor electrical conductivity of MOFs in electrolytes.Ananoscale MOF, Co 0.24 Ni 0.76 -bpa-200, possessing ultrahigh stability with uncommon semiconductor behavior (s = 4.2 10 À3 Sm À1 )w as fabricated. The MOF comprises ar obust hydrophobic paddlewheel and an optimized Co/Ni ratio,with consequent control over MOF size and the degree of conjugation of the coligand. AD FT study revealed that appropriate Ni 2+ doping reduces the activation energy of the system, thus providing ah igher carrier concentration, and the strongly delocalized N-donor ligand notably increases the metal-ligand orbital overlap to achieve efficient charge migration, leading to continuous through-bond (-CoNi-N-CoNi-) 1 conduction paths.These structural features endow the MOF with agood cycling stability of 86.5 %(10 000 cycles) and ahigh specific capacitance of 1927.14 Fg À1 among pristine MOF-based electrodes.

It is a tremendous challenge to prepare solvent-free dense energetic metal-organic frameworks (EMOFs), hence also to improve their stability and energetic performance. In this study, based on in situ microcalorimetry, an interpenetrating EMOF without solvent molecules, [Cu(tztr)] (1, Htztr = 3-(tetrazol-5-yl)triazole) was obtained, possessing high stability (T = 360 °C) and outstanding energetic properties (ΔH = 7.53 kcal cm, D = 8.429 km s, P = 40.02 GPa).