THE INTRAMOLECULAR AROMATIC-RING STACKING INTERACTION OF MIXED LIGAND PALLADIUM(Ⅱ)COMPLEXES Ⅲ.STUDIES ON THE Pd^(2+)-A-UTP^(4-)SYSTEMS BY HNMR

The intramolecular aromatic-ring stacking interaction of mixed- ligand complex Pd(A)(UTP)^(2-)in the system pd^(2+)-A-UTP^(4-)has been determined by ~1HNMR,where A=1,10-phenanthroline(phen),2,2'-bipyridyl(bpy)and DL- tryptophan(trp^-);UTP^(4-)=uridine 5-triphosphate.The result indicates that it is the partial stacking between the uracil ring of UTP^(4-)and the heterocyclic ring of A that makes H(5),H(6)and H(1')in the UTP^(4-)shift upfield signifi- cantly.Accordingly,the order of aromatic-ring interaction in the mixed- ligand complex has been obtained as follows:Pd(phen)(UTP)^(2-)(?)Pd(bpy)(UTP)^(2-) Pd(trp)(UTP)^(3-).

Studies of the Intramolecular Aromatic-ring Stacking Interactions in the Ternary Platinum(Ⅱ) Complexes

The stability constants of some ternary mixed-ligand complexes, Pt(Phen)(CA)+, where Phen=1,10-phenanthroline and CA- =carboxylate, were determined by means of potentiometric pH titration in aqueous solutions(I=0.1 mol/L, KNO 3; 25 ℃), and the stability of them was compared with that of the corresponding binary complexes. It was revealed that the ternary complexes containing phenylalkane carboxylates ligands(PCA-) are much more stable than those formed with formate and acetate. The results indicate that there exist the intramolecular aromatic-ring interactions between the phenanthroline ring of Phen and the phenyl moiety of ligand PCA- in the ternary mixed-ligand Pt(Phen)(PCA)- complexes. The extent of the stacking interactions, which depends on the number of methylene groups between the phenyl moieties and the coordinated phenylalkane carboxylate groups, was calculated. The best-fitted stack was obtained for the complexes with 2-phenylacetate and 3-phenylpropionate as the ligands.

Intramolecular aromatic-ring stacking interaction of ternary Zn(UTP)L^(2-) complexes

THE mechanism of the action of the classic platinum antitumor drugs can be interpreted accord-ing to their bidentate, bifunctional interaction with the DNA of the tumor cell, resulting in in-hibition of the DNA replication. Recently, it was found that a new class of compounds withthe general formula cis-[Pt（NH3）2（N-het）Cl]Cl（N-het is a heteroaromatic N-base like pyri-dine） show effective antitumor activities. However, two possible mechanisms of action

THE INTRAMOLECULAR AROMATIC-RING STACKING INTERACTION OF THE TERNARY MIXEDLIGAND COMPLEXES:STUDY OF Pd^(2+)-HETEROCYCLIC RING BASE-NUCLEOTIDE SYSTEM BY POTENTIOMETRIC pH TITRATION

One of the typical phenomena of intramolecular ligand-ligand interaction in complexes is the aromatic-ring stacking which depends on the stacking of those non-coordinating aromatic rings. Since 1974 H. Sigel reported that the stacking interaction was observed between pyridine ring of bpy（bpy=2, 2′-bipyridyl） and purine ring of ATP4-(ATP4-=adenosine 5′-triphosphate) among the mixed-ligand Cu（bpy） （ATP）2- complexes. The study on this field has been extended to a large amount of ligands such as nucleotides, xanthosines,

AROMATIC-RING STACKING INTERACTIONS BETWEEN LIGANDS IN THE TERNARY MIXED LIGAND COMPLEXES——M^(2+) (Co^(2+), Ni^(2+))-PHEN-HCA SYSTEM

So far, more attention was paid to the fact that the kind, position and properties of the substituted radicals of coordinating or non-coordinating groups in the complexes exert an important influence on the stability of the complexes, but less to the interaction between those non-coordinating groups. Although the existence of hydrogen bonds between ligands and the formation of covalent and ionic bonds have been reported, it is only about ten

Synthesis, molecular structure and intramolecular aromatic-ring stacking interaction of a novel binuclear Cu(Ⅱ) complex with 1, 10-phenanthroline and phenylacetate

The complex [Cu(phen)2(POAc)3]ClO·4H2O has been synthesized and investigated by elemental analysis, IR spec-troscopy and X-ray diffraction methods, where phen = 1,10-phenanthroline, POAc = phenylacetate group). The complex crystallizes in the triclinic space group PI with two molecules in a unit cell of dimensions a = 1.0579(2) nm, b = 1.2423(3) nm, c = 1.9190(4) nm, α = 71.84(1)°, β = 80.50(2)°, γ = 88.60(1)°, V = 2.3625(9) nm3, R = 0.0407 and Rw = 0.0656. The complex results from bridging of two Cu(phen)2+ units by three carboxylate groups, and each Cu2+ ion is in a distorted square pyramidal geometry with two nitrogen atoms of phen and three carboxylate oxygen atoms of POAc. It has been showed that intramolecular stacking interactions occur between the phenyl moieties of POAc and aromatic rings of phen, leading to a novel molecule structure with two coordinating modes of carboxylate ligands, of which two phenylacetates are μ2-carboxylate-O-bridging ligands, and the other is a μ2-carboxylate-O, O'-bridging ligand.

Enhanced photochemical oxidation ability of carbon nitride by π-πstacking interactions with graphene

A one-pot method for the preparation of g-C3N4/reduced graphene oxide（rGO） composite photocatalysts with controllable band structures is presented.The photocatalysts are characterized by Fouirer transform infrared spectroscopy,X-ray diffraction,scanning electron microscope,transmission electron microscope,and Mott-Schottky analysis.The valance band（VB） of g-C3N4 exhibits a noticeable positive shift upon hybridizing with rGO,and thus results in a strong photo-oxidation ability.The g-C3N4/rGO composites show a higher photodegradation activity for 2,4-dichlorophenol（2,4-DCP） and rhodamine B（RhB） under visible light irradiation（λ≥420 ran）.The g-C3N4/rGO-1sample exhibits the highest photocatalytic activity,which is 1.49 and 1.52 times higher than that of bulk g-C3N4 for 2,4-DCP and 1.52 times degradation,respectively.The enhanced photocatalytic activity for g-C3N4 originates from the improved visible light usage,enhanced electronic conductivity and photo-oxidation ability by the formed strong π-π stacking interactions with rGO.

Studies on Intramolecular Stacking Interaction of Ternary Complexes M（Ⅱ）（ATP）￣（2－） with Heteroaromatic N－Base Ligands

o understand the driving forces leading to mixed-ligand complexes in biologi-cal systenis.ternary complexes of M (ATP(L￣(2-) type, where M = Cu￣(2+), Ni￣(2+) orCo￣(2+) , and L= pyridine(Py) , 4-picoline, 3, 5-lutidine, isoquinoline (lq) or benzimi-dazole(Bi) in aqueous solution were studied by spectropliotometry, some of them(M=Cu￣(2+), L = isoquinoline or benzimidazole) were also separately studied hy po-tentiometric pH titration. The results show that an intramolecular stacking interac-tion exists between the heteroaromatic ring of the ligands and the purine moiety ofATP.

A New Cadmium(Ⅱ) Coordination Polymer Extended through Hydrogen Bonds and π-π Stacking Interactions: Synthesis and Photoluminescence Property

A new coordination polymer, {[Cd(OPY)(tdc)(HO)]·H2 O}n(OPY = 4,4?-(oxybis(4,1-phenylene))dipyridine, H2 tdc = thiophene-2,5-dicarboxylic acid), has been synthesized hydrothermally based on a V-shaped ligand OPY. The structure was fully characterized by elemental analysis, FT-IR spectroscopy, and X-ray single-crystal diffraction analysis. In1, two OPY ligands and one water molecule acted as terminal ligands coordinating to Cdcation to form [Cd(OPY)HO]units, which are then linked by tdc2-ligands to generate a one-dimensional chain. Every two adjacent chains linked by extensive O–H···O hydrogen bonds constitute one-dimensional double-chains, and such chains are extended into two-dimensional layers via O–H···N hydrogen bonds. These layers are further connected to form a three-dimensional supramolecular architecture via π-π stacking interactions. In addition, the thermal stability and solid state fluorescence property of 1 were also investigated.

A Silver Complex of 6,7-Dicyanodipyridoquinoxaline:π-Stacking Interactions and Luminescence

The reaction of 6,7-dicyanodipyridoquinoxaline （DICNQ） with AgNO3 in a 1：1 molar ratio by solution method gave a new complex [Ag（DICNQ）2]NO3 1. Single-crystal X-ray diffraction analysis reveals that the complex crystallizes in the space group Ibca of orthorhombic system with eight formula units in a cell. Crystal data for 1： a = 15.7055（17）, b = 18.411（2）, c = 20.680（2）A, V = 5979.7（11）A3, Z = 8, C32Hl2AgN13O3, Mr = 734.42, Dc = 1.632 g/cm3, μ= 0.734 mm-1, F（000） = 2928, S = 1.023 and T= 293（2） K. The final R = 0.0659 and wR = 0.1927 for 2118 observed reflections with I 〉 2σ（I）, and R = 0.0801 and wR = 0.2196 for all data. The complex builds up a packing structure by π-π stacking interactions and shows a luminescent feature.

Thermal Stability Improved by π–π Stacking Interactions: Synthesis, Crystal Structure and Thermal Decomposition of Sodium Nitroformate

An energetic salt, sodium nitroformate （NaNF）, was synthesized and characterized by elemental analysis, IR and UV spectra, and its crystal structure was first determined by single crystal X-ray diffraction. The structure exhibits two types of π-π stacking interactions between the nitroformate anions, i e, the parallel-displaced and T-shaped confgurafions. Furthermore, the thermal decomposition mechanism was investigated by DSC, TG-DTG and FTIR techniques. The kinetic parameters of the thermal decomposition were also calculated by using Kissinger＇s and Ozawa-Doyle＇s methods. The results show that NaNF has a good thermal stability, which is attributed to the π-π stacking interactions.

A model study on the stacking interaction of phenanthroline ligand with nucleic acid base pairs: An ab initio, MP2 and DFT studies

The stacking of phenanthroline(phen) ligand within base pair sequences is one of the important factors for the stabilization of metalphen complex within DNA. The stacking ability of this ligand has been assessed to deduce the base pair selectivity as well as to identify the favored region of intercalation. Different level of theories have been used to predict the favorable regions for stacking interaction of phen ligand with base pair, but the results of MP2/6-31+G(d,p) is found to be reasonably good for monitoring such interactions.

STUDY ON THE STABILITY AND STACKING INTERACTION EFFECT OF THE TERNARY M(Ⅱ)(ATP)AND PYRIDINE-LIKE LIGANDS

The stabilities of the complexes of three pyridine-like ligands with M(II)(ATP)^(2-) and M(II)(M=Ni,Co)were studied by spectrophotometry and by comparing the stability constants of the ternary complexes with these of the binary complexes.A stacking interaction between the pyridine ring and the purine ring of ATP is indicated.The general existence of the stacking interaction encourages us to interpret the antitumor mechanism of a new class of antitumor drugs.

CNDO Studies on the Intermolecular Coulomb Interaction in TCNQ-Stack

The coulomb interaction among TCNQ- molecules in different stack structures was calculated by quantum chemistry CNDO method. The results of the calculation would be used to explain the change rule of the electricity property of the TCNQ complex very well.

Influence of non-covalent interactions on properties of lanthanide systems with aromatic ligands

Two series of lanthanide compounds, namely, chlorides containing different numbers of both 1,10-phenanthroline （Phen） molecules and chloride anions in the first coordination sphere, and Schiff Bases （SBs） derived from Pyridoxal （PL） and amino acids, were characterized by single crystal X-ray diffraction and luminescence techniques. The combined use of these techniques for the analysis of long-distance europium non-covalent interactions was performed for the first time. As a result, the correlation between supramolecular organization and the features of the Eum electronic transitions was found for the compounds of the first series. Strong non-covalent interactions between pyridoxal tings of SBs （the second series of compotmd） led to the formation of 1：2 species and four-dentate coordination function of these SBs in aqueous solution.

Unveiling chain–chain interactions in CO2-based crystalline stereocomplexed polycarbonates by solid-state NMR spectroscopy and DFT calculations

CO2-based stereocomplexed polycarbonates derived from the intermolecularly interlocked interaction between the enantiopure polymers with the opposite configuration exhibit high crystallinity, excellent thermal and mechanical stabilities. Deep insights into the mechanism of stereocomplexation are of particular importance to the design and manufacture of new promising and sustainable polycarbonates with enhanced physicochemical properties. Our solid-state NMR experiments linking with DFT computations clearly reveal the specific chain-chain interactions in a typical stereocomplexed poly（4,4-dimethyl-3,5,8-trioxabicyclo[5.1.0] octane carbonate）（PCXC）.13C CP/MAS NMR,1H DUMBO MAS NMR and 13C/1H relaxation-time measurements indicate that the formation of stereocomplex reduces the local mobilities of carbonyl, methine and methylene groups in each chain of PCXC significantly. Through a combination of two-dimensional 1H-13C HETCOR NMR and DFT calculation analysis, the cis-/trans-conformations and packing models of PCXC chains in the amorphous, enantionpure isotactic and stereocomplexed polycarbonates are identified. The splitting of 13C and 1H NMR chemical shifts of methine groups in the backbone carbon region demonstrates the ordered interlock interactions between the R-and S-chain in the stereocomplexed PCXC.

Unusual F_(3)stacking fault in magnesium

An unusual F_(3)basal stacking fault resulting from twin-dislocation interaction in magnesium is observed in molecular dynamics simulation.The F_(3)fault is produced in the twin lattice from the interaction between a migrating(1012)twin boundary and a partial dislocation of either a prismatic<c>edge,or a prismatic<c+a>mixed dislocation in the matrix.The condition is that the partial dislocation needs to have a negative sign and lie on a plane intersecting a compression site of the twin boundary.The F_(3)fault can also be generated when a positive basal<a>mixed dislocation in the twin lattice,with slip plane intersecting a compression site of the twin boundary,interacts with a basal-prismatic twinning disconnection.The F_(3)fault comprises two I_(1) faults that have the same character but are separated by two basal layers.It has one end connected to the twin boundary,and the other end bounded by a lattice defect with a Burgers vector identical to that of a 30°Shockley partial dislocation.The formation frequency of the F_(3)fault is higher at a lower shear stress(below∼400 MPa)and/or a lower temperature(100 K and 200 K).The F_(3)fault can decompose into a glissile 30°Shockley and a T_(2) fault at a temperature above∼400 K.The relationships between the F_(3)fault and other types of basal stacking faults such as I_(2),T_(2) or paired I_(1) faults that are separated by multiple basal layers are discussed.

A robust self-healing polyurethane elastomer: From H-bonds and stacking interactions to well-defined microphase morphology

Self-healing materials have attracted considerable attention because of their improved safety, lifetime, energy efficiency and environmental impact. Supramolecular interactions have been extensively considered in the field of self-healing materials due to their excellent reversibility and sensitive responsiveness to environmental stimuli. However,development of a polymeric material with good mechanical performance as well as self-healing capacity is very challenging. In this study, we report a robust self-healing polyurethane(PU) elastomer polypropylene glycol-2-amino-5-(2-hydroxyethyl)-6-methylpyrimidin-4-ol(PPG-mUPy) by integrating ureidopyrimidone(UPy) motifs with a PPG segment with a well-defined architecture and microphase morphology.To balance the self-healing capacity and mechanical performance, a thermal-triggered switch of H-bonding is introduced. The quadruple H-bonded UPy dimeric moieties in the backbone induce phase separation to form a hard domain as well as enable further aggregation into microcrystals by virtue of the stacking interactions, which are stable in ambient temperature. This feature endows the PU with high mechanical strength. Meanwhile, a high healing efficiency can be realized, when the reversibility of the H-bond was unlocked from the stacking at higher temperature. An optimized sample PPG1000-mUPy50%with a good balance of mechanical performance(20.62 MPa of tensile strength) and healing efficiency(93% in tensile strength) was achieved. This strategy will provide a new idea for developing robust self-healing polymers.

Self-energy and interaction energy of stacking fault in fcc metals calculated by embedded-atom method

The stacking fault energies of five fcc metals (Cu, Ag, Au, Ni and Al) with various quantivalences have been calculated by embedded-atom method (EAM). It indicated that the stacking fault energy is mainly determined by the metallic bond-energy and the lattice constant. Thus, monovalent fcc metals should have different stacking fault energies, contracy to Attree’s conclusion. The interaction energy between stacking faults one {111} layer apart in a fcc metal is found to be 1/40–1/250 of its self-energy, while it becomes zero when the two stacking faults are two layers apart. The twin energy is just half of the energy of intrinsic stacking fault energy without the consideration of lattice relaxation and the energy of a single intrinsic stacking fault is almost the same as that of extrinsic stacking fault, which are consistent with the results from the calculation of Lennard-Jones force between atoms, but differ from Attree’s result.