Hydrothermal Synthesis and Crystal Structure of a Square Grid Coordination Copper(II) Polymer from 1,4-Bis(imidazole-1-ylmethyl)benzene

The title compound [Cu（bix）2（NO3）z·H2P]n 1 （bix = 1,4-bis（imidazole-1-ylme-thyl） benzene） has been synthesized by hydrothermal method. Its crystal structure is of monoclinic, space group P1^- with a = 8.3075（13）, b = 9.4725（13）, c = 10.0192（13） A, α = 91.088（4）, β = 104.063（6）, γ = 101.88（1）, V = 746.5（3） A^3, Z = 1, C28H30N10O7Cu1, Mr = 682.16, Dc = 1.518 g/cm^3, μ = 0.796 mm^-1, F（000） = 353, the final R = 0.0535 and wR = 0.0996 for 2921 observed reflections with I 〉 2σ（I）. Each bix ligand binds two Cu（Ⅱ） ions to form a 2-D（4,4） square grid layer, which is connected by hydrogen bonds showing large channels occupied by solvated water molecules and nitrate anions.

INFLUENCE OF SERIES OF SQUARE GRIDS ON FRACTAL DIMENSIONS-A Case Study of Mountains of China's Mainland

MANDELBROT enunciated the uncertainty of the length of a coastline in his paper "How long is the coastline of Britain?" published in Science in 1967. The fractal concept was presented for the first time in that paper and has been applied to many fields ever since. Although fractal dimensions of lots of phenomena were calculated by the box-counting method,the quantitative influence of series of square grids on them is ignored. The issue is systematically discussed as a case study of the mountains of China′s Mainland in this paper. And some significant conclusions are drawn as follows: 1) Although the fractal character objectively exists in the mountains of China′s Mainland,and it does not vary with the changes of series of square grids,the fractal dimensions of the mountains of China′s Mainland are different with these changes. 2) The fractal dimensions of the mountains of China′s Mainland vary with the average lengths of sides of series of square grids. The fractal dimension of the mountains of China′s Mainland is the function of the average length of side of square grid. They conform to the formula D=f(r) (where D is the fractal dimension,and r is the average length of side of square grid). 3) Different dots of data collection can affect the fractal dimension of the mountains of China′s Mainland. 4) The same range of length of side of square grid and dots of data collection can ensure the comparison of fractal dimensions of the mountains of China′s Mainland. The research is helpful to get the more understanding of fractal and fractal dimension,and ensure that the fractal studies would be scientific.

Integrative square-grid triboelectric nanogenerator as a vibrational energy harvester and impulsive force sensor

A square-grid triboelectric nanogenerator （SG-TENG） is demonstrated for harvesting vibrational energy and sensing impulsive forces. Each square of the three-dimensional （3D）-printed square grid is filled with an aluminum （A1） ball. The grid structure allows the SG-TENG to harvest vibrational energy over a broad bandwidth and operate at different vibrational angles. The most striking feature of the SG-TENG is its ability of being scaled and integrated. After connecting two SG-TENGs in parallel, the open-circuit voltage and short-circuit current are significantly increased over the full vibrational frequency range. Being integrated with a table tennis racket, the SG-TENG can harvest the vibrational energy from hitting a ping pong ball using the racket, where a direct hit by the racket generates an average output voltage of 10,9 ~ 0.6 V and an average output current of 0.09 ± 0.02 boA. Moreover, the SG-TENG integrated into a focus mitt can be used in various combat sports, such as boxing and taekwondo, to monitor the frequency and magnitude of the punches or kicks from boxers and other practitioners. The collected data allow athletes to monitor their status and improve their performance skills. This work demonstrates the enormous potential of the SG-TENG in energy harvesting and sensing applications.

Synthesis of two lanthanide clusters Ln^(Ⅲ)_(4)(Gd_(4) and Dy_(4)) with [2×2] square grid shape:Magnetocaloric effect and slow magnetic relaxation behaviors

Two isostructural tetranuclear lanthanide clusters named [Ln_(4)(L)_(4)(CH_(3) O)_(4)]·CH_(3) OH(Ln=Gd(Ⅲ) for 1,Dy(Ⅲ) for 2,H_(2) L=N’-(2-hydroxy-3-methoxybenzylidene)-6-(hydroxymethyl) picolinohydrazide) were successfully isolated by using a polydentate Schiff based ligand and Ln(Ⅲ) nitrate salts.The structures of 1 and 2 were characterized by X-ray structural analyses,they are held by four double deprotonated ligands L2-.In them all the lanthanide ions are eight-coordinated and distributed over four vertices of a parallelogram,presenting a Ln4 cluster with a strict [2 × 2] square grid pattern.The details of magnetic analysis show that 1 displays weak anti-ferromagnetic exchange between neighboring Gd(Ⅲ) ions through carboxylate oxygen and methanol oxygen ligand atoms.Furthermore,1 exhibits significant magnetocaloric effect with the maximum entropy change-ΔSm value of 28.5 J/(kg K) for ΔH=7.0 T at 2.0 K.For compound 2,remarkable slow magnetic relaxation behaviors are observed in the presence of zero magnetic field with τ0=1.02 × 10^(-6) s and energy barrier ΔE/kB=43.24 K.