Spectroscopic fingerprints for charge localization in the organic semiconductor (DOEO)4[HgBr4]·TCE

Changes of the electronic structure accompanied by charge localization and a transition to an antiferromagnetic ground state were observed in the organic semiconductor (DOEO)4 [HgBr4 ]·TCE. Localization starts in the temperature region of about 150 K and the antiferromagnetic state occurs below 60 K. The magnetic moment of the crystal contains contributions of inclusions (droplets), and individual paramagnetic centers formed by localized holes and free charge carriers at 2 K. Two types of inclusions of 100–400 nm and 2–5 nm sizes were revealed by transmission electron microscopy. Studying the temperature-and angular dependence of electron spin resonance (ESR) spectra revealed fingerprints of antiferromagnetic contributions as well as paramagnetic resonance spectra of individual localized charge carriers. The results point on coexistence of antiferromagnetic long and short range order as evident from a second ESR line. Photoelectron spectroscopy in the VUV, soft and hard X-ray range shows temperature-dependent effects upon crossing the critical temperatures around 60 K and 150 K. The substantially different probing depths of soft and hard X-ray photoelectron spectroscopy yield nformation on the surface termination. The combined investigation using complementary methods at the same sample eveals the close relation of changes in the transport properties and in the energy distribution of electronic states

Research and Design of a Routing Protocol in Large-Scale Wireless Sensor Networks

无线传感器网络，作为全球未来十大技术之一，集成了传感器技术、嵌入式计算技术、分布式信息处理和自组织网技术，可实时感知、采集、处理、传输网络分布区域内的各种信息数据，在军事国防、生物医疗、环境监测、抢险救灾、防恐反恐、危险区域远程控制等领域具有十分广阔的应用前景。 本文研究分析了无线传感器网络的已有路由协议，并针对大规模的无线传感器网络设计了一种树状路由协议，它根据节点地址信息来形成路由，从而简化了复杂繁冗的路由表查找和维护，节省了不必要的开销，提高了路由效率，实现了快速有效的数据传输。 为支持此路由协议本文提出了一种自适应动态地址分配算——ADAR（AdaptiveDynamicAddre...As one of the ten high technologies in the future, wireless sensor network, which is the integration of micro-sensors, embedded computing, modern network and Ad Hoc technologies, can apperceive, collect, process and transmit various information data within the region. It can be used in military defense, biomedical, environmental monitoring, disaster relief, counter-terrorism, remote control of haz...学位：工学硕士院系专业：信息科学与技术学院通信工程系_通信与信息系统学号：2332007115216

The first photochromic bimetallic assemblies based on Mn(III) and Mn(II) Schiff-base (salpn, dapsc) complexes and pentacyanonitrosylferrate

International audienceFour cyano-bridged bimetallic complexes, \[Mn(salpn)](2)[Fe(CN)(5)NO]\(n) (1), \[Mn(salpn)(CH3OH)](4)[Mn(CN)(5)NO]\[C(CN)(3)]center dot 3H(2)O (2), \[Mn(dapsc)][Fe(CN)(5)NO]center dot 0.5CH(3)OH center dot 0.25H(2)O\(n) (3) and \[Mn(salpn)(CH3OH)](4)[Fe(CN)(5)NO]\(ClO4)(2)center dot 4H(2)O (4), where salpn(2-) = N, N'-1,3-propylene-bis(salicylideneiminato) dianion and dapsc = 2,6-diacetylpyridine-bis(semicarbazone), have been synthesized and structurally characterized by single crystal X-ray diffraction. In 1, the nitroprusside anion [Fe(CN)(5)NO](2-) coordinates with four [Mn(salpn)](+) via four co-planar CN- groups, whereas each [Mn(salpn)](+) links two [Fe(CN)(5)NO](2-) ions, which results in a two-dimensional network. The structure of 3 contains two independent neutral infinite chains \[Mn(dapsc)][Fe(CN)(5)(NO)]\(infinity) consisting of alternating cationic [Mn-II(dapsc)](2+) and anionic [Fe-II(CN)(5)(NO)](2-) units connected through cyanide bridges. The cation complexes 2 and 4 have a pentanuclear molecular structure in which four [Mn(salpn)(MeOH)](+) fragments are linked by the [Mn(CN)(5)NO](3-) or [Fe(CN)(5)(NO)](2-) moieties, respectively. The magnetic and photochromic properties of 1 and 3 have been studied. The thermal magnetic behaviour of the complexes indicates the presence of weak antiferromagnetic interactions between Mn3+ or Mn2+ mediated by diamagnetic [Fe(CN)(NO)-N-5](2-) bridges. Irradiation of 1 and 3 with light gives birth to the long-lived metastable states of nitroprusside

Zero-Field Slow Magnetic Relaxation in Binuclear Dy Acetylacetonate Complex with Pyridine-N-Oxide

A new complex [Dy(C5H7O2)3(C5H5NO)]2·2CHCl3 (1) has been synthesized by the reaction of pyridine-N-oxide with dysprosium (III) acetylacetonate in an n-heptane/chloroform mixture (1/20). X-ray data show that each dysprosium atom is chelate-like coordinated by three acetylacetonate ligands and the oxygen atom from two bridging molecules of pyridine-N-oxide, which unite the dysprosium atoms into a binuclear complex. Static (constant current) and dynamic (alternating current) investigations and ab initio calculations of the magnetic properties of complex 1 were performed. The complex was shown to exhibit a frequency maximum under alternating current. At temperatures above 10 K, the maximum shifts to a higher frequency, which is characteristic of SMM behavior. It is established that the dependence of ln(τ) on 1/T for the relaxation process is nonlinear, which indicates the presence of Raman relaxation mechanisms, along with the Orbach mechanism

Synthesis, Structure, and Magnetic Properties of 1D {[Mn^III(CN)₆][Mn^II(dapsc)]}_<i>n</i> Coordination Polymers: Origin of Unconventional Single-Chain Magnet Behavior

Two one-dimensional cyano-bridged coordination polymers, namely, {[Mn^II(dapsc)]­[Mn^III(CN)₆]­[K­(H₂O)_2.75(MeOH)_0.5]}_<i>n</i>·0.5<i>n</i>(H₂O) (<b>I</b>) and {[Mn^II(dapsc)]­[Mn^III(CN)₆]­[K­(H₂O)₂(MeOH)₂]}_<i>n</i> (<b>II</b>), based on alternating high-spin Mn^II(dapsc) (dapsc = 2,6-diacetylpyridine bis­(semicarbazone)) complexes and low-spin orbitally degenerate hexacyanomanganate­(III) complexes were synthesized and characterized structurally and magnetically. Static and dynamic magnetic measurements reveal a single-chain magnet (SCM) behavior of <b>I</b> with an energy barrier of <i>U</i>_eff ≈ 40 K. Magnetic properties of <b>I</b> are analyzed in detail in terms of a microscopic theory. It is shown that compound <b>I</b> refers to a peculiar case of SCM that does not fall into the usual Ising and Heisenberg limits due to unconventional character of the Mn^III–CN–Mn^II spin coupling resulting from a nonmagnetic singlet ground state of orbitally degenerate complexes [Mn^III(CN)₆]^3–. The prospects of [Mn^III(CN)₆]^3– complex as magnetically anisotropic molecular building block for engineering molecular magnets are critically analyzed

Mononuclear Heptacoordinated 3d-Metal Helicates as a New Family of Single Ion Magnets

The series of Co(II), Fe(II), and Ni(II) mononuclear coordination compounds of [CoL(NCS)2]·3DMSO (1), [CoL(H2O)2](ClO4)2·DMSO (2), [CoL(H2O)(EtOH)][CoCl4]·2H2O (2a), [FeL(NCS)2]·DMSO (3), and [NiL(NCS)2]·CH3CN (4) composition (where L is 2,6-bis(1-(2-(4,6-dimethylpyrimidin-2-yl)hydrazineylidene)ethyl)pyridine), with an [MLA2] coordination unit (where A is a pair of apical monodentate ligands), was synthesized. In compounds 1, 2, 2a, and 3, the ligand L is pentadentate, and cobalt and iron ions are placed in a heavily distorted pentagonal pyramidal coordination environment, while in 4 the Ni(II) ion is hexacoordinated. Easy plane-type magnetic anisotropy (D = 13.69, 11.46, 19.5, and 6.2 cm−1 for 1, 2, 2a, and 4, respectively) was established for cobalt and nickel compounds, while easy axis-type magnetic anisotropy (D = −14.5 cm−1) was established for iron compound 3. The cobalt coordination compounds 1 and 2 show SIM behavior under a 1500 Oe external magnetic field, with effective magnetization reversal barriers of 65(1) and 60(1) K for 1 and 2, respectively. The combination of Orbach and Raman relaxation mechanisms was shown to adequately describe the temperature dependence of relaxation times for 1 and 2. CASSCF/NEVPT2 calculations were performed to model the parameters of the effective spin Hamiltonian for the compounds under study

Single-Ion Magnet Et₄N[Co^II(hfac)₃] with Nonuniaxial Anisotropy: Synthesis, Experimental Characterization, and Theoretical Modeling

In this article we report the synthesis and structure of the new Co­(II) complex Et₄N­[Co^II­(hfac)₃] (<b>I</b>) (hfac = hexafluoroacetylacetonate) exhibiting single-ion magnet (SIM) behavior. The performed analysis of the magnetic characteristics based on the complementary experimental techniques such as static and dynamic magnetic measurements, electron paramagnetic resonance spectroscopy in conjunction with the theoretical modeling (parametric Hamiltonian and ab initio calculations) demonstrates that the SIM properties of <b>I</b> arise from the nonuniaxial magnetic anisotropy with strong positive axial and significant rhombic contributions