Kinetic Study on the Induced Coordination Reaction of Lanthanum with p-Acetylcarboxylazo

The absorption spectra of p-ACA(p-acetylcarboxylazo)and its complex with lanthanum ions were determined.The molar ratio of metal to ligand in the complex was estimated to be 1:2.An induction period was found existing in the coordination reaction between La and p-ACA and the effects of temperature,acidity and ionic strength on the induction period were studied.The reaction mechanism was depicted.The rate equation is consistent with the rate law,R=k[La(H_2O)_6^(3+)][H_3O^+],obtained by kinetic method.Finally the possible geometric structure of this complex was discussed.

Kinetic Studies on Axial Coordination Reaction of Tetraphenylporphinatocobalt（Ⅱ） Chloride

he axial coordination reactions of tetraphenylporphinatocobalt (Ⅲ) chloride(Co TPPC1) with various imidazoles RIm ( HIm . imidazole; Melm , 2-methylimida-zole) were investigated in acetone and dichloromethand solvents at different temper-atures. The reaction mechanisms were proposed and the differences between experi-mental results in the two solvents h ave been interpreted using the proposed mecha-nisms and rate equations for the first time , and the reaction scheme for the axial re-action of the metalloporphyrin has been developed. Hydrogen bonding plays an im-portant role in the reactions. The effects of various imidazoles for these reactionsand the solvents are reported. The comparison between iron and cobalt porphyrinsin the kinetics are discussed.

Thermodynamic study of axial coordination reaction of zinc porphyrin with metal Schiff base and imidazole complex

A thermodynamic study is reported for the coordination reaction of ZnT ( m-X)PP derivatives (X = NO2, Cl, OCH3, H or CH3) with various ligands L (L= imidazole (Im), 2-methylimidazole (Melm), clotrimidazole (CIM), imidazol-4-carboxaldehyde (4-CHOIm), unsymmetrical tetradentate copper Schiff base, Culm(p-C1), Ch(p-Br), and nickel Schiff base, Nilm(p-CI)), in dichloromethane solvent. Conversion of the four-coordinated ZnT( m-X)PP to the five-coordinated species is followed and isosbestic behavior is exhibited in the region among 450 and 700 nm. The reaction of a copper(II) or nickel(II) imidazolate Schiff base with ZnT( m-X)PP results in the formation of an imidazolate bridged heterobinuclear complex. The stochiometric number is unity for all axial ligands. The equilibrium constants were determined using the β band of ZnT( m-X)-PP in the 293–308 K range by the method of Rose and Drago. It increases with decrease in temperature, and ΔH0 0, Δ09 0. The stronger the nucleophilic ability of the axial ligand is, the larger the stability of the axial coordination product is. Hammet linear relationships and isoequilibrium relationships exist in the system studied.

STUDIES ON SOLID STATE REACTIONS OF COORDINATION COMPOUNDS(LXⅡ)Solid state synthesis and crystal structure of the complex ICu_(0.84)Au_(0.16)(PPh_3)_2(SC(Ph)NHPh)CIJ·0.5CS_2

[Cu_(0.84)Au_(0.16)(PPh_3)_2(SC(Ph)NHPh)Cl]·0.5CS_2=,Mr=895.79,monoclinic,space group P2_1/a,a=17.231(3),b=14.611(2),c=18.000(3) ,β=105.56(2)°,V=4365(1) ~3, Z=4,D_c=1.37g/cm^3.,λ(MoK_α)=0.71073 ,μ=12.15cm^(-1),F(000)=1855,R=0.052, R_W=0.045 for 3930 observed reflections with Ⅰ>1.5σ(Ⅰ).The central metal atom has a dis. torted tetrahedral geometry with bond lengths Cu-S=2.384(2) (Au-S=2.389(4)), Cu-Cl=2.481(3)(Au-Cl=2.474(1))and Cu-P=2.269(2)-2.289(2)(Au-P=2.270(4)-2.279(4)) .

Regulating single-atom Mn sites by precisely axial pyridinic-nitrogen coordination to stabilize the oxygen reduction

Designing single-atom catalysts for oxygen reduction reaction(ORR)are fashionable but challenging to boost the zinc-air battery performance.Significantly enhanced ORR activity by manganese(Mn)singleatom catalysts can be achieved by accurately regulating the coordination number of isolated Mn atoms.Theoretical calculations indicate that the single Mn-N5sites possess lower free energy barrier and higher oxygen adsorption performance than single Mn-N4sites to accelerate the ORR kinetics.Target to it,here we synthesize an atomically dispersed Mn-N5catalyst by precisely axial coordination of pyridinic-N doped into two-dimensional(2D)porous nanocarbon sheets(~3.56 nm thickness),which reveals outstanding catalytic activity and ultrahigh stability for the ORR in zinc-air battery owing to the inhomogeneous charge distribution of Mn-N5sites compared to the conventional single-site Mn-N4catalyst and Pt/C.This work gives a new strategy for in situ regulating the electronic structure of metal single-atoms and further promoting the overall ORR performance in energy systems.

A Theoretical Study on Nonadiabatic Trapping Models of the Reaction NH+H←→N+H_2

The properties of nonadiabatic trapping models of the reaction NH+H -N+H, are investigated in a collinear model as \veil as a non-collinear thermal reaction on the basis of theintrinsic reaction coordinate (IRC) intbrmation obtained by ah initio calculations at QCISD/631 IG** ie\el. Using the unitied statistical theory fornonadiabatic trapping models. the thermal rateconstants over the temperature range of 2000-3000K are computed which are in excellent agreementwith the experiment results.

Theoretical Study on Dehydrogenation Reactions of Silanol

The pathway of dehydrogenation reaction of silanol SiH3OH is investigated by ab initio Mo calculations using RHF/-31G basis set. The geometries of reactant, transition states and products are optimized on the singlet potential energy surface of the ground state. The activation energies, reaction heats, statistical A factor and activation entropies are calculated. The vibrational analysis of the reactant and the transition states is made. The reaction crgodography along the intrinsic reaction coordinate (IRC) are performed to examine the reaction mechanism.

Reaction Coordinates by Nonlinear Dimensionality Reduction

Deriving reaction coordinates for the characterization of chemical reactions has long been a demanding task.In our previous work[ACS Cent.Sci.3,407(2017)],the reaction coordinate of a(retro-)Claisen rearrangement in aqueous solution optimized through a Bayesian measure,a linear combination of bond lengths formation and breakage,was judged to be optimal among all trails.Here,considering the nonlinearity of the transition state,we use isometric mapping and locally linear embedding to obtain one reaction coordinate which is composed of a few collective variables.With these methods,we find a more reasonable and powerful one-dimensional reaction coordinate,which can well describe the reaction progression.To explore the reaction mechanism,we analyze the contribution of intrinsic molecular properties and the solventsolute interactions to the nonlinear reaction coordinate.Furthermore,another coordinate is identified to characterize the heterogeneity of reaction mechanisms.

Calculation of the Canonical Rate Constant for the Nonadiabatic Trapping Model Based on Unified Statistical Theory:A Test on The Exchange Reaction H_2+H

A new approach was employed to calculate the canonical (thermal) rate constant basedon unified statistical theory. All information for the calculation was obtained from ab initio meth-ods. The flux integral for any point of reaction coordinate was calculated by counting the numberof quantum states and applied to determine the dividing surfaces along the intrinsic reaction coor-dinate (IRC). The classical exchange reaction H2+H, as an example, was investigated. The IRC forthe reaction has been traced and detailed information of IRC was carried out at the QCISD/6-311 G** level .The calculated rate constants are well consistent with the experimental results.

Temperature-dependent Hydrothermal Synthesis of Two Distinct Three-dimensional Copper Complexes

Two distinct copper coordination polymers, namely [Cu^Ⅱ2（2,5-pydc）2（bpp）2]·H2O（1） and Cu2^ⅠCu^Ⅱ（2,5-pydc）2（bpp）2（2）（2,5-pydc = pyridine-2,5-dicarboxylic acid, bpp = 1,3-bi（4-pyridyl）propane）, have been successfully synthesized through hydrothermal conditions under different temperatures. Single-crystal X-ray structural analysis revealed that both complexes 1 and 2 are 3D frameworks. Complex 1 is an 8-connected 2-fold interpenetrating network based on [Cu（2,5-pydc）]4 molecular building block（MBB）, and also can be simplified as a 4-connected net if the Cu（Ⅱ） ion is regarded as an independent node, whereas 2 shows a（4,4）-connected non-interpenetrated framework which contains mixed valence Cu（Ⅰ/Ⅱ） centers. The results demonstrate that temperature plays a significant role in the final structures of the complexes.

Photo-isomerization of Aromatic α-Hydroxy Hydrazone

Photo-isomerization of aromatic α-hydroxy hydrazone was reported. We investigated the structures of salicylaldehyde phenylhydrozone（SP） in the ground state using density functional theory（DFT） with the B3LYP functional and the 6-311＋G（d） basis set. All nine possible isomers of SP in the ground state consist of seven phenol forms and two ketone forms. Intrisic reaction coordinate（IRC） analysis discloses the existence of a cycle driven by the two proton transfer processes in the ground and excited states of SP, which suggests that no ketonic form could exist in the ground state. Further theoretical studies of the potential energy surfaces support a trans-cis conversion followed by a relaxation to the stable form of SP in the excited states.

Hydrogen Generation by Splitting H2O Molecule on the Pt6Cu Cluster

Seven reaction paths for hydrogen generation from water molecule with Pt6Cu cluster are identified, based on the density functional theory with exchange-correlation functional in Becke＇s three-parameter form. The complex structures of the reactant H2O@Pt6Cu and the structures of the products H2＋O@Pt6Cu and H＋OH@Pt6Cu on various adsorption sites of Pt6Cu cluster are optimized and the energy stability of the structures is confirmed by frequency analysis. The geometries of the transition states and the intrinsic reaction coordinate are also determined at the same theoretical level. The energy barrier for each reaction is calculated. The results demonstrate that the Pt6Cu cluster can abstract one H atom from H2O molecule with one step reaction by overcoming a moderate energy barrier. These findings can be helpful for understanding the mechanism to produce hydrogen from a water molecule with Pt6Cu cluster.

Studies on the solid state reactions of coordination conpounds——XLⅤⅢ.The effect of KSCN on the thermal decomposition of cobalt(Ⅲ)-ammine complexes

The evolved gaseous analysis (EGA),infrared spectra,and XRD have been applied to the study of solid state reactions of KSCN with five cobalt(Ⅲ)-ammine complexes:[Co- (NH_3)_5N_3]Cl_2,[Co(NH_3)_5(NO_2)]Cl_2,[Co(NH_3)_5(H_2O)]Cl_3,[Co(NH_3)_5Cl]Cl_2,and [Co(NH_3)_6]Cl_3 in a hydrogen atmosphere.It is found that the existence of KSCN shifts the thermal decom- position of these complexes to a lower temperature.The corresponding peak temperatures are near 140℃.The effect of KSCN is discussed and kinetic parameters of deammine reactions are calculated.

Indoor multi-robot intelligent coordination based on omni-directional visible light communication

Multi-robot coordination （MRC） is a key challenge for complex artificial intelligence systems, and conventional wireless-communication-based MRC mechanisms that cannot be deployed in radio-frequency-limited environ- ments. In this Letter, we present a promising solution that utilizes indoor omni-directional visible light communication （VLC） technology to realize efficient multi-robot intelligent coordination （MRIC）. The specific design is presented along with the implemental details of a practical MRIC experimental platform. The exper- imental results show that a 50 Mb/s on-off-keying-based omni-directional VLC can be realized with an effective distance of 2.3 m and a bit error rate of 〈10^-6 in the proposed MRIC platform.

A Novel Tetraphenylethylene-Based“Turn On”Fluorescent Sensor with Highly Sensitive Response to Mercury Ions

A novel 4-tert-butyl-N’-(4-(1,2,2-triphenylvinyl)benzylidene)benzohydrazide(TBB)was successfully synthesized in simple one-step process.It was characterized by FT-IR,1H NMR,13C NMR and HRMS.Its fluorescence sensing ability to 15 metal ions was investigated.Weak emission from TBB could be efficiently increased by trace Hg^2+,through coordination reaction between TBB and Hg^2+ with"turn on"character.The fluorescence intensity of TBB/Hg^2+([TBB]=3.0×10^–6 mol/L,[Hg2+]=1.3×10^–4 mol/L)was 7.5 times higher than that of TBB.This TBB sensor exhibited high selectivity for Hg^2+ and other metal ions did not interfere in this determination.The limit of detection was 0.566μmol/L(S/N=3).The experimental results showed that this TBB sensor could sensitively respond to Hg^2+ within concentration range(from 5×10–6 mol/L to 1.3×10^–4 mol/L).

Comparative studies on the mechanism of uridine phosphorolysis

We have used quantum mechanical method to study the transition states(TSs) of uridine phosphorolysis reaction. Comparing the four different reaction pathways and the five transition states obtained, we conclude that enzymatic uridine phosphorolysis takes place mainly according to acid-catalyzed S(N)2 mechanism. The proposed reaction pathway is consistent with many experimental results.

Quantum chemical study on the thermal rearrangements of HNCRCR'CO

MINDO/3 molecular orbital theory has been used to study the thermal rearrangements of HNCRCR'CO.The results obtained show that the activation energy of this rearrangement depends on the migrating group R and the group R'.

A quantum chemical study on the mechanism of the consecutive addition of HCN to propionitrile

MINDO/3 MO method has been used to study the mechanism of the consecutive addition of HCN to propionitrile. The results obtained for the first five steps show that the reaction is exothermic, and step 1 is the rate determining step.

Kinetic Study and NBO Analysis of the Dehydrogenation Mechanism of Five-membered Ring Heterocyclic 2,5-Dihydro-[furan, thiophene, selenophene]

The theoretical study of the dehydrogenation of 2,5-dihydro-[furan （1）, thiophene （2）, and selenophene （3）] was carried out using ab initio molecular orbital （MO） and density functional theory （DFT） methods at the B3LYP/6-311G＊＊//B3LYP/6-311G＊＊ and MP2/6-311G＊＊//B3LYP/6-311G＊＊ levels of theory. Among the used methods in this study, the obtained results show that B3LYP/6-311G＊＊ method is in good agreement with the available experimental values. Based on the optimized ground state geometries using B3LYP/6-311G＊＊ method, the natural bond orbital （NBO） analysis of donor-acceptor （bond-antibond） interactions revealed that the stabilization energies associated with the electronic delocalization from non-bonding lone-pair orbitals [LP（e）x3] to C＊C（1）- H（2） antibonding orbital, decrease from compounds 1 to 3. The LP（e）x3→σ＊c（1）-H（2） resonance energies for compounds 1--3 are 23.37, 16.05 and 12.46 kJ/mol, respectively. Also, the LP（e）xa→σ＊c（1）-H（2） delocalizations could fairly explain the decrease of occupancies of LP（e）x3 non-bonding orbitals in ring of compounds 1-3 （3 〉2 〉 1）. The electronic delocalization from LP（e）x3 non-bonding orbitals to σ＊c（1）-G（2） antibonding orbital increases the ground state structure stability, Therefore, the decrease of LP（e）x3→σ＊c（1）-H（2） delocalizations could fairly explain the kinetic of the dehydrogenation reactions of compounds 1-3 （kl〉k2〉k3）. Also, the donor-acceptor interactions, as obtained from NBO analysis, revealed that the πc（4）=c（7）→σ＊c（1）-H（2） resonance energies decrease from compounds 1 to 3. Further, the results showed that the energy gaps between πC（4）-C（7） bonding and σ＊c（1）-H（2） antibonding orbitals decrease from compounds 1 to 3. The results suggest also that in compounds 1--3, the hydrogen elimi- nations are controlled by LP（e）→σ＊ resonance energies. Analysis of bond order, natural bond orbital charges, bond indexes, synchronicity parameters, and IRC calculations indicate that these reactions are occurring through a con- certed and synchronous six-membered cyclic transition state type of mechanism.