排序方式: 共有65条查询结果,搜索用时 15 毫秒
1.
2.
3.
Manolis M. Antonakis Alexandra Tsirigotaki Katerina Kanaki Constantinos J. Milios Spiros A. Pergantis 《Journal of the American Society for Mass Spectrometry》2013,24(8):1250-1259
In this study, we report on the development of a novel nebulizer configuration for sonic-spray ionization (SSI) mass spectrometry (MS), more specifically for a version of SSI that is referred to as Venturi easy ambient sonic-spray ionization (V-EASI) MS. The developed nebulizer configuration is based on a commercially available pneumatic glass nebulizer that has been used extensively for aerosol formation in atomic spectrometry. In the present study, the nebulizer was modified in order to achieve efficient V-EASI-MS operation. Upon evaluating this system, it has been demonstrated that V-EASI-MS offers some distinct advantages for the analysis of coordination compounds and redox active inorganic compounds over the predominantly used electrospray ionization (ESI) technique. Such advantages, for this type of compounds, are demonstrated here for the first time. More specifically, a series of labile heptanuclear heterometallic [CuII 6LnIII] clusters held together with artificial amino acid ligands, in addition to easily oxidized inorganic oxyanions of selenium and arsenic, were analyzed. The observed advantages pertain to V-EASI appearing to be a “milder” ionization source than ESI, not requiring electrical potentials for gas phase ion formation, thus eliminating the possibility of unwanted redox transformations, allowing for the “simultaneous” detection of negative and positive ions (bipolar analysis) without the need to change source ionization conditions, and also not requiring the use of syringes and delivery pumps. Because of such features, especially because of the absence of ionization potentials, EASI can be operated with minimal requirements for source parameter optimization. We observed that source temperature and accelerating voltage do not seem to affect labile compounds to the extent they do in ESI-MS. In addition, bipolar analysis of proteins was demonstrated here by acquiring both positive and negative ion mass spectra from the same protein solutions, without the need to independently adjust solution and source conditions in each mode. Finally, the simple and efficient operation of a dual-nebulizer configuration was demonstrated for V-EASI-MS for the first time. Figure
? 相似文献
4.
Carretta S Guidi T Santini P Amoretti G Pieper O Lake B van Slageren J El Hallak F Wernsdorfer W Mutka H Russina M Milios CJ Brechin EK 《Physical review letters》2008,100(15):157203
We study the spin dynamics in two variants of the high-anisotropy Mn6 nanomagnet by inelastic neutron scattering, magnetic resonance spectroscopy and magnetometry. We show that a giant-spin picture is completely inadequate for these systems and that excited S multiplets play a key role in determining the effective energy barrier for the magnetization reversal. Moreover, we demonstrate the occurrence of tunneling processes involving pair of states having different total spin. 相似文献
5.
Cano J Cauchy T Ruiz E Milios CJ Stoumpos CC Stamatatos TC Perlepes SP Christou G Brechin EK 《Dalton transactions (Cambridge, England : 2003)》2008,(2):234-240
DFT calculations reveal the unusual ferromagnetic exchange observed in an oxo-centered Mn(III) triangle may originate from a combination of the 'non-planarity' of the bridging oxime ligands and the non-parallel alignment of the Jahn-Teller axes. 相似文献
6.
Moro F Corradini V Evangelisti M De Renzi V Biagi R del Pennino U Milios CJ Jones LF Brechin EK 《The journal of physical chemistry. B》2008,112(32):9729-9735
We study the magnetic properties of two new functionalized single-molecule magnets belonging to the Mn 6 family (general formula [Mn (III)6O2(R-sao)6(O2C-th)2L(4-6)], where R=H (1) or Et (2), HO2C-th=3-thiophene carboxylic acid, L=EtOH, H2O and saoH2 is salicylaldoxime) and their grafting on the Au(111) surface. Complex 1 exhibits spin ground-state S=4, as the result of ferromagnetic coupling between the two antiferromagnetic Mn (III) 3 triangles, while slight structural changes in complex 2, switch the dominant magnetic exchange interactions from anti- to ferromagnetic, enhancing the spin ground-state to S=12 and, consequently, the effective energy barrier for the relaxation of magnetization. Direct-current and alternating-current magnetic susceptibility measurements show that the functionalized complexes preserve the main magnetic properties of the corresponding not-functionalized Mn 6 clusters (i.e., total spin value and magnetic behavior as a function of temperature), though a reduction of the anisotropy barrier is observed in complex 2. For both complexes, the -O2C-th functionalization allows the direct grafting on Au(111) surface by liquid-phase deposition. X-ray photoemission spectroscopy demonstrates that the stoichiometry of the molecular cores is preserved after grafting. Scanning tunneling microscopy (STM) reveals a sub-monolayer distribution of isolated clusters with a slightly higher coverage for complex 1. The cluster stability in the STM images and the S-2p energy positions demonstrate, for both derivatives, the strength of the grafting with the gold surface. 相似文献
7.
8.
Milios CJ Inglis R Bagai R Wernsdorfer W Collins A Moggach S Parsons S Perlepes SP Christou G Brechin EK 《Chemical communications (Cambridge, England)》2007,(33):3476-3478
The complex [Mn(6)O(2)(Et-sao)(6)(O(2)C(11)H(15))(2)(EtOH)(6)] has U(eff) = 80 K. 相似文献
9.
Milios CJ Inglis R Vinslava A Prescimone A Wernsdorfer W Parsons S Perlepes SP Christou G Brechin EK 《Chemical communications (Cambridge, England)》2007,(26):2738-2740
The spin ground state of a [Mn(III)(6)Mn(II)(2)] cluster has been deliberately switched from S = 1 to S = 7 upon designed ligand substitution. 相似文献
10.
Shaw R Laye RH Jones LF Low DM Talbot-Eeckelaers C Wei Q Milios CJ Teat S Helliwell M Raftery J Evangelisti M Affronte M Collison D Brechin EK McInnes EJ 《Inorganic chemistry》2007,46(12):4968-4978
We report the synthesis, by solvothermal methods, of the tetradecametallic cluster complexes [M14(L)6O6(OMe)18Cl6] (M=FeIII, CrIII) and [V14(L)6O6(OMe)18Cl6-xOx] (L=anion of 1,2,3-triazole or derivative). Crystal structure data are reported for the {M14} complexes [Fe14(C2H2N3)6O6(OMe)18Cl6], [Cr14(bta)6O6(OMe)18Cl6] (btaH=benzotriazole), [V14O6(Me2bta)6(OMe)18Cl6-xOx] [Me2btaH=5,6-Me2-benzotriazole; eight metal sites are VIII, the remainder are disordered between {VIII-Cl}2+ and {VIV=O}2+] and for the distorted [FeIII14O9(OH)(OMe)8(bta)7(MeOH)5(H2O)Cl8] structure that results from non-solvothermal synthetic methods, highlighting the importance of temperature regime in cluster synthesis. Magnetic studies reveal the {Fe14} complexes to have ground state electronic spins of S相似文献