Square-planar mixed ligand nickel dithiolenes as second-order non-linear chromophores: synthesis and characterisation of [Ni(Me<Subscript>2</Subscript>pipdt)(dddt)]

Abstract  The novel [Ni(Me₂pipdt)(dddt)] complex based on the Me₂pipdt (1,4-dimethylpiperazine-3,2-dithione) and dddt (5,6-dihydro-1,4-dithine-2,3-dithiolate) ligands has been synthesised and characterised. Structural data, vibrational marker, solvatochromic behaviour of the typical absorption in the near infrared region, and approximate theoretical calculations suggest that an unbalanced electron distribution at the dithiolene core occurs in the ground and excited states. In particular, the dddt ligand gives a prevailing contribution to the HOMO, and Me₂pipdt to the LUMO. The charge-transfer character of the HOMO–LUMO transition makes this complex a potential second-order non-linear optic chromophore. Graphical Abstract        

Evidence for the dimer-of-(mixed-valent dimers) configuration in tetranuclear {(μ<Subscript>4</Subscript>-TCNX)[Ru(NH<Subscript>3</Subscript>)<Subscript>5</Subscript>]<Subscript>4</Subscript>}<Superscript>8+</Superscript>, TCNX = TCNE and TCNQ,from DFT calculations

Abstract  DFT calculations of the complex ions {(μ₄-TCNX)[Ru(NH₃)₅]₄}⁸⁺, TCNX = tetracyanoethene (TCNE) and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ), yield triplet state energy minimum structures with nonplanar bridging ligands. The calculated C–C bond distances and twist angles confirm considerable metal-to-ligand electron transfer from the metal centers to the TCNE and TCNQ bridges in the lowest triplet and singlet states. The resulting situation, involving a weak interaction between two strongly coupled malonodinitrilato-bridged Ru^2.5Ru^2.5 entities (Class III), agrees with experimental results; the near-orthogonality found for the ground states of the molecular ions explains the observed magnetic exchange coupling between two S = 1/2 sites, the 1,258 cm⁻¹ absorption in the IR spectrum of the TCNE complex, and the reversible two-electron oxidation. The nitrile stretching frequency shifts were reasonably reproduced by the calculations. A density-of-states representation for the TCNQ complex shows a rather different electronic structure in comparison to that for the formally related {(μ₄-TCNQ)[Re(CO)₃(bpy)]₄}⁴⁺, in particular a different frontier orbital situation. In contrast to the (TCNQ⁰)(Re^I)₄ situation, the tetraruthenium species with an approximate (TCNX²⁻)(Ru^2.5)₄ formulation represent unconventional mixed-valent tetranuclear compounds; in other words, weakly coupled pairs of strongly coupled dinuclear moieties. EPR spectroscopy at the W band frequency (95 GHz) of the TCNE compound confirms that the reduction of the complex leads to the oxidation of TCNE²⁻ to yield a (TCNE^•−)(Ru^II)₄ species. Graphical abstract  

On Combinatorics of Schrödinger Perturbations

We give a tight upper bound for Schrödinger-type perturbations of integral kernels.     

A Mono‐Cobalt Substituted Wells–Dawson Phosphotungstate with an Antenna Ligand

A mono‐cobalt substituted Wells–Dawson polyoxometalate with an antenna ligand linked to the Co^II atom, was prepared by reaction of the mono‐vacant Wells–Dawson precursor [P₂W₁₇O₆₁]^10– with a imidazole‐cobalt complex by using the bench method. It was isolated as the imidazole salt: (HIm)₇H[P₂W₁₇O₆₁Co(Im)] · 4H₂O ( 1 ) (Im = imidazole). Compound 1 was characterized by elemental analysis, IR and UV/Vis spectroscopy, TG analysis, cyclic voltammetry and single‐crystal/powder X‐ray diffraction. This is the first example of the 3d transition metal mono‐substituted Wells–Dawson polyoxometalate with an antenna ligand.     

Synthesis,structural characterisation and thermal decomposition of a new organic–inorganic hybrid material (C5H14N2)[Cu(SO4)2(H2O)4] · H2O

The crystal structure of copper sulfate templated by 2-methylpiperazine, (C₅H₁₄N₂)[Cu(SO₄)₂(H₂O)₄] · H₂O, was investigated using single crystal X-ray diffraction data. At room temperature, it crystallises in the monoclinic P2₁/n space group with the following unit-cell parameters: a = 6.9153(1), b = 23.1295(3), c = 10.4472(1) Å, β = 104.227(1)°, V = 1619.75(4) Å³ and Z = 4. The Cu^II cation adopts a slightly distorted octahedral geometry, arising from four water molecules and two sulfate tetrahedra leading to the formation of [Cu(SO₄)₂(H₂O)₄] units. The structure consists of isolated [Cu(SO₄)₂(H₂O)₄]²⁻ anions, 2-methylpiperazinediium cations (C₅H₁₄N₂)²⁺ and water molecules connected by a three-dimensional hydrogen-bond network. The thermal decomposition of the precursor, studied by thermogravimetry and temperature-dependent X-ray powder diffraction, proceeds through four stages giving rise to the copper oxide.     

High Pressure Phase Stability of Ti with Self-consistent ab initio Lattice Dynamics Approach

The traditional quasiharmonic approximation cannot predict the phase diagram of Ti accurately, due to the well-known soften phonon modes of the β-Ti. By means of self-consistent ab initio lattice dynamics (SCAILD) method, in which the effects of phonon-phonon interactions are considered, the phonon dispersion relations at finite temperature for Ti are calculated. From the phonon dispersions, we extrapolat the acoustic velocities and harmonic elastic constants. The dynamical stable regions and phase diagram of Ti are also predicted successfully. The results show that SCAILD method can be designed to work for strongly anharmonic systems where the QHA fails.     

Influence of Chemical Environment on the Optical Properties in Transition Metal Ions Doped Materials

The sensibility of luminescent properties in transition metal doped materials to the matrices' chemical environment is explained in this paper, this is because of their strong phonon-electron coupling which are caused by the 3d electrons exposed nature. The influence of the chemical environments on the Mn²⁺-doped materials' optical properties, including the structure type of coordinate polyhedron, the polyhedral bridge linking manner and the lattice parameter, was illustrated in detail in this work. The impact of crystal field strength parameter (10 Dq) on the maximum energy differentiae in spontaneous emission band of Cr³⁺:⁴T_2g→⁴A_2g and in excited state absorption band ⁴T_2g→⁴T_1g (⁴F), and covalent bond intension's impact on the optical properties of Os⁴⁺ were also analyzed. This work's purpose is to discover the principle of the sensibility character, then we can use it to optimal the design of materials in order to find the excellent luminescent materials for practical utilization.     

Rotational analysis and line intensities of the HCO band at 296 K

This paper computes the rotational energy levels of the HCO transition, especially, the higher values of the rotational quantum numbers N_{Ka Kc} and K_a, with the rotational constants which are obtained via B3LYP method with 6-311G basis set, and the results show that the calculated frequencies using the computed vibration--rotation energy levels are in reasonable agreement with the data from the experiment. Meanwhile, the line intensities of HCO are first reported, the results are of significance for the studying HCO.     

Structural and magnetic properties of MoS2 monolayer zigzag nanoribbon doped by Ti,V, Cr,and Mn

In order to find new functions of monolayer MoS₂ in nanoelectronics or spin electronic devices, using spin-polarized density functional theory (DFT) calculations with on-site coulomb interaction (U), we investigated substitutional doping of Mo atoms of monolayer zigzag MoS₂ nanoribbon (ZZ-MoS₂ NR) by transition metals (TM) (where TM = Ti, V, Cr, Mn) at the Mo-edge, S-edge, and the middle of the NRs. The results of this study indicate the NR widened irrespective of the doped TM position and type, and the Mo-edge was found as the easiest substitutional position. For ZZ-MoS₂ NR doped by Mn, Cr or V atoms, the preferred magnetic coupling state is the edge atoms of S at the S-edge, exhibiting the same spin polarization with TM (named the FM1 state), attributing the NR with metallic magnetism. For Ti-doped monolayer ZZ-MoS₂ NR, in addition to the FM1 state, other preferred magnetic coupling state was observed in which the edge atoms of S at the S-edge exhibit the opposite spin polarization with that of Ti (named the FM2 state). Thus, the NR doped by Ti atom possesses metallic (FM1 state) or half-metallic (FM2 state) magnetism. The total magnetic moments of the ZZ-MoS₂ NR doped by TM follows a linear relationship as a function of the TM dopants (Mn, Cr, V, and Ti). Under $>4\text{\%}$ applied strain, the NR doped by Ti atom only presents the characteristics of half-metallic magnetism as the initial one in the FM2 state, and its total magnetic moment always remained 0 μB, i.e., it was not affected by the width of the NR. This study provides a rational route of tuning the magnetic properties of ZZ-MoS₂ NRs for their promising applications in nanoelectronics and spin electronic devices.