Direct evidence of quantum coherence in a single-molecule magnet in frozen solution is reported with coherence times as long as T2 = 630 ± 30 ns. We can strongly increase the coherence time by modifying the matrix in which the single-molecule magnets are embedded. The electron spins are coupled to the proton nuclear spins of both the molecule itself and interestingly, also to those of the solvent. The clear observation of Rabi oscillations indicates that we can manipulate the spin coherently, an essential prerequisite for performing quantum computations.PACS numbers: 75.30.Gw, 75.50.Xx, The key concept in quantum information processing is that a quantum bit (qubit) may be not just 0 or 1, as in ordinary computer bits, but an arbitrary superposition of 0 and 1. This means that any two-level system, that can be put into a superposition state, is a qubit candidate [1]. The required superposition state is created by electromagnetic radiation pulses with a frequency corresponding to the energy splitting between the two levels ( Fig. 1c). The contribution of each of the two levels to the superposition state has a cyclic dependence on the pulse length, leading to so-called Rabi oscillations [1]. The observation of such oscillations is a proof-of-principle for the viability of performing quantum computations with a particular system. Quantum computers will probably not be realized from single atoms but will most likely utilize solid state devices, such as superconducting junctions, semiconductor structures, or molecular magnets [1,2]. For these large systems the quantum coherence decays fast, which drastically shortens the time available for quantum computation. Molecular magnets have been considered as qubits because they can be easily organized into large-scale ordered arrays by surface self-assembly [? ], and because they possess excited electronic-spin states required for two-qubit gate operations [5,6]. Single-molecule magnets (SMMs) are exchange-coupled clusters with highspin ground states [3]. The Ising-type anisotropy creates an energy barrier toward magnetization relaxation [ Fig. 1(b)], and many fascinating quantum phenomena have been observed in these systems, such as quantum tunnelling of the magnetization and quantum phase interference [3]. The large splitting of the two lowest states of SMMs in zero field (in principle) allows performing coherent spin-manipulations without external magnetic field, which simplifies any practical implementation. SMMs have also been proposed for the implementation of Grover's algorithm [2] allowing numbers between 0 and 2 2S−2 to be stored in a single molecule.The long coherence time is a crucial first step towards successful implementation of SMMs as qubits [1]. Therefore, recent years have seen a great deal of activity in trying to determine the quantum coherence times in SMMs, which was estimated to be of the order of 10 ns [7,8,9,10]. In several cases, energy gaps between superposition states have been reported that are larger than the expected decoherence energy scale [...

The syntheses and structures of two decametallic mixed-valent Mn supertetrahedra using 2-amino-2-methyl-1,3-propanediol (ampH2), two decametallic mixed-valent Mn planar discs using 2-amino-2-methyl-1,3-propanediol (ampH2) and 2-amino-2-ethyl-1,3-propanediol (aepH2), and a tetradecametallic mixed-valent Mn planar disc using pentaerythritol (H4peol) are reported. The decametallic complexes display dominant ferromagnetic exchange and spin ground states of S = 22, and the tetradecametallic complex displays dominant antiferromagnetic exchange and a spin ground state of S = 7 +/- 1. All display large (the former) and enormous (the latter) magnetocaloric effect--the former as a result of negligible zero-field splitting of the ground state, and the latter as a result of possessing a high spin-degeneracy at finite low temperatures--making them the very best cooling refrigerants for low-temperature applications.

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1-Phenyl-3-trifluoromethyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl is the first example of a hydrazyl radical that shows a reversible sharp spin transition fully completed within 5(1) K. The nominally first-order transition takes place at ca. 58(2) K and proceeds via subtle changes of intra- and interstack interactions between two similar structural phases. The low-temperature phase (5-60 K) is diamagnetic and has a singlet ground state (2Jexp = -166.8 cm(-1), gsolid = 2.0042, ρ = 0.2%) stemming from a multicenter two-electron interaction. The high-temperature phase (60-300 K) is paramagnetic as a result of noninteracting S = 1/2 spins arising from weakly bound dimers.

Novel silver(I) metallo-drugs of the nonsteroidal anti-inflammatory drug nimesulide (nim) and the mitochondriotropic triaryl derivatives of pnictogen ligands (tpE, E = P (tpp, tptp, or totp), As (tpAs), Sb (tpSb)) with the formulas {[Ag(nim) (tpp)2]DMF} (1), [Ag(nim) (tptp)2] (2), [Ag(nim) (totp)] (3), [Ag(nim) (tpAs)2] (4), and [Ag(nim) (tpSb)3] (5) ((tpp = triphenyphosphine, tptp = tri(p-tolyl)phosphine, totp = tri(o-tolyl)phosphine, tpAs = triphenylarsine, tpSb = triphenylantimony, and DMF = dimethylformamide) were synthesized and characterized by melting point, vibrational spectroscopy (mid-Fourier transform IR), (1)H NMR, UV-visible spectroscopic techniques, and X-ray crystallography. The in vitro cytotoxic activity of 1-5 against human breast adenocarcinoma cancer cell lines: MCF-7 (estrogen receptor (ER) positive) and MDA-MB-231 (ER negative) was determined. The genotoxicity on normal human fetal lung fibroblast cells (MRC-5) caused by 1-5 was evaluated by fluorescence microscopy. The absence of micronucleus in MRC-5 cells confirms the in vitro non toxicity behavior of the compounds. Because of the morphology of the cells, an apoptotic pathway was concluded for the cell death. The apoptotic pathway, especially though the mitochondrion damage, was confirmed by DNA fragmentation, cell cycle arrest, and permeabilization of the mitochondrial membrane tests. The molecular mechanism of action of 1-5 was further studied by (i) the binding affinity of 1-5 toward the calf thymus (CT) DNA, (ii) the inhibitory activity of 1-5 against lipoxygenase (an enzyme that oxidizes polyunsaturated fatty acids to leukotrienes or prostaglandins), and (iii) the catalytic activity of 1-5 on the oxidation of linoleic acid (an acid that partakes in membrane fluidity, membrane enzyme activities, etc.) to hyperoxolinoleic acid by oxygen.