pH-Dependent Excited-State Properties of N,N-di(2-phosphonoethyl)-1,4,5,8-naphthalenediimide

Abstract— The effect of the protonation state of a novel aqueous soluble N,N'-di(2-phosphonoethyl)-l,4,5,8-naphthalene-diimide (DPN) on its spectroscopic properties is studied. In aqueous solution DPN depicts linear Lambert-Beer plots up to the solubility limits at pH 1.0, 7.1 and 10.1, in accordance with its solubilization as a monomer. A small increase in the extinction coefficients with pH is observed. Conversely a strong decrease in the fluorescence emission yields are observed with the increase in pH. These results are shown to originate from the distinct efficiencies of the intersystem crossing of DPN as a function of the net charge on the phosphono moieties. Accordingly, from the decrease in fluorescence emission, titration curves were obtained resulting in two pKa of –1.5 and 6.7 in agreement with the potentiometric analysis. In parallel monitoring the amount of heat deposited in the system shows an inverse pattern, that is, increase in the thermal tensing time-resolved signal with pH. Laser flash photolysis and thermal Iensing data in the absence and presence of oxygen show the interplay of an intersystem crossing process with the protonation state of the dye. The changes in protonation from neutral to two- and four-fold charged species are accompanied by an enhancing effect on the naphthalenediimide ring toward spin inversion (triplet formation) and consequently in different fluorescence yields     

Anionic N-heterocyclic carbenes with N,N'-bis(fluoroaryl) and N,N'-bis(perfluoroaryl) substituents

A series of rhodium complexes, [Rh(cod)(NHC-F(x))(OH(2))] (cod = 1,5-cyclooctadiene; NHC = N-heterocyclic carbene), incorporating anionic N-heterocyclic carbenes with 2-tert-butylmalonyl backbones and 2,6-dimethylphenyl (x = 0), 2,6-difluorophenyl (x = 4), 2,4,6-trifluorophenyl (x = 6), and pentafluorophenyl (x = 10) N,N'-substituents, respectively, has been prepared by deprotonation of the corresponding zwitterionic precursors with potassium hexamethyldisilazide, followed by immediate reaction of the resulting potassium salts with [{RhCl(cod)}(2)]. These complexes could be converted to the related carbonyl derivatives [Rh(CO)(2)(NHC-F(x))(OH(2))] by displacement of the COD ligand with CO. IR and NMR spectroscopy demonstrated that the degree of fluorination of the N-aryl substituents has a considerable influence on the σ-donating and π-accepting properties of the carbene ligands and could be effectively used to tune the electronic properties of the metal center. The carbonyl groups on the carbene ligand backbone provided a particularly sensitive probe for the assessment of the metal-to-ligand π donation. The ortho-fluorine substituents on the N-aryl groups in the carbene ligands interacted with the other ligands on rhodium, determining the conformation of the complexes and creating a pocket suitable for the coordination of water to the metal center. Computational studies were used to explain the influence of the fluorinated N-substituents on the electronic properties of the ligand and evaluate the relative contribution of the σ- and π-interactions to the ligand-metal interaction.     

Spectroscopy study on the photochromism of Schiff bases N,N'-bis(salicylidene)-1,2-diaminoethane and N,N'-bis(salicylidene)-1,6-hexanediamine

The photochromism of Schiff bases N,N'-bis(salicylidene)-1,2-diaminoethane (BSE) and N,N'-bis(salicylidene)-1,6-cyclohexanediamine (BSH) was studied by steady-state and time-dependent fluorescence, UV Vis absorption spectroscopy and theoretical chemistry calculations. The experimental results show that BSH can perform the photochromism easier than BSE, may be due to the molecular topology difference.     

Platinum (II) phosphine complexes with acetylene ligands containing 1,4,5,8-naphthalenediimide: Synthesis, crystal structure and electrochemistry

A new acetylene ligand modified with the electron-accepting 1,4,5,8-naphthalenediimide group and its Pt(II) phosphine complexes are reported. The Pt(II) complexes incorporate optical properties of the imide group, and display two reversible imide-centred reduction processes.     

Synthesis and characterization of N,N'-bis[2-hydroxyethyl]-1,4,6,8-naphthalenediimide with para substituted of phenols based on charge-transfer complexes

The interaction of charge-transfer (CT) complexes resulted from the reaction of N,N'-bis[2-hydroxyethyl]-1,4,6,8-naphthalenediimide (BHENDI) with some various acceptors like as substituted phenols in para position; 4-aminophenol (4AP), 4-methylphenol (4MP) and 4-nitrophenol (4NP) have been studied in methanol at room temperature. The reaction was studied using electronic (UV-vis), mid infrared, and (1)H NMR spectra and thermal measurements (TGA and DTG) as well as elemental analysis CHN. The chemical analysis data of the resulted CT-complexes, BHENDI-acceptors, reveal that the formation of a 1:2 CT complexes in all cases. The interaction of N,N'-bis[2-hydroxyethyl]-1,4,6,8-naphthalenediimide and phenolic acceptors were investigated spectrophotometrically and found two detected CT bands have n-pi(*) transition. The donor site involved in CT interaction is the diimide two nitrogen atoms by forming hydrogen bonding. The kinetic thermodynamic parameters like DeltaE, DeltaH, DeltaS and DeltaG are calculated from the DTG diagrams using Coats-Redfern method. The electrical conductivity properties for the solid CT complexes were measured within the temperature of room 25 degrees C.     

N,N'-bis(substituted phenyl)-1,2,4,5-benzenetetracarboxylic-1,2:4,5-diimides

The preparation of N,N'-bis(substituted phenyl)-1,2,4,5-benzenetetracarboxylic-1,2:4,5-di-imides by the reaction of 1,2,4,5-benzenetetracarboxylic-1,2:4,5-dianhydride ( 1 ) with aryl-amines and with aryl isocyanates is described. Correlations are made between the properties of these diimides and the nature and position of the substituents in the phenyl ring. The condensation of dianhydride 1 with diisocyanates yields polymers varying from soft elastomers to tough films, depending upon the amount of imide structure in the polymer chain.     

Trinuclear lanthanide complexes of a compartmental ligand N,N'-bis(2-pyridinyl)-2,6-pyridinedicarboxamide: a spectroscopic investigation

Trinuclear lanthanide complexes of the formula [Ln(3)(PPDA)(NO(3))(6)(H(2)O)(2)].NO(3).2H(2)O where Ln=La(III), Pr(III), Sm(III), Nd(III), Eu(III) Gd(III) Tb(III), Dy(III) and Y(III); H(2)PPDA=N,N'-bis(2-pyridinyl)-2,6-pyridinedicarboxamide, have been isolated. The complexes were characterized by elemental analyses, conductivity measurements, magnetic susceptibility measurements and spectral (IR, NMR, UV-vis, fluorescence, FAB and EPR) and thermal studies.     

Synthesis and Crystal Structure of N,N'-bis(2-aminoethyl)-2,4-pentanediiminatogold(III) Perchlorate

A synthetic procedure is described for N,N^'-bis(2-aminoethyl)-2,4-pentanediiminatogold(III) perchlorate. The complex was investigated by X-ray phase and X-ray diffraction analyses, electron spectroscopy, and IR spectroscopy. Crystal data for C₉H₁₉AuN₄Cl₂O₈: a = 10.093(2), b = 7.1740(10), c = 22.985(5) , = 90.35(3)°, V = 1664.2(5) ³, space group P2(1)/n, Z = 4, d _calc = 2.324 g/cm³. The structure consists of nearly planar acyclic cations [C₉H₁₉AuN₄]²⁺ and perchlorate anions [ClO₄]^–. The C–C and C–N bonds inside the -diiminate ring are delocalized. The parameters of the [C₉H₁₉AuN₄]²⁺ cation are compared with those in related complexes. The compound is stable in air for at least half a year; solubility in water is 0.8%.     

Coated wire silver-ion selective electrode based on a N,N'-bis(2-thienylmethylene)-1,2-diaminobenzene.

A novel membrane coated platinum-wire electrode (MCPWE) based on N,N'-bis(2-thienylmethylene)-1,2-diaminobenzene (BTMD) for highly selective determination of Ag+ ion has been developed. The influences of membrane composition and pH on the potentiometric responses of electrode were investigated. The potentiometric responses are independent of the pH of the test solution in the range of 5.0 - 9.0. The electrode shows a linear response for Ag+ ion over the concentration range of 1.0 x 10(-60 to 1.0 x 10(-1) M with a lower detection limit of 6.0 x 10(-7) M. The electrode possesses a Nernstian slope of 59.7 mV decade(-1) and a fast response time of < or = 17 s and can be used for at least 2 months without any observable deviation. The proposed electrode displayed very good selectivity for Ag+ ion with respect to NH4+ and alkali, alkaline earth and some common transition metal ions. The practical utility of the electrode has been demonstrated by its use as the indicator electrode in the potentiometric titration of an AgNO3 solution with a NaI solution and in determination of the silver content of a developed radiological film.     

Extraction behavior of divalent first row transition metal ions with N,N'-bis(2-hydroxyphenylmethyl)-N,N'-bis(2-pyridylmethyl)-1,2-ethanediamine and its derivatives

For the fundamental study on the development of novel extractants, extraction behavior of divalent first row transition metals such as manganese, nickel, copper and zinc was studied with using N,N'-bis(2-hydroxyphenylmethyl)-N,N'-bis(2-pyridylmethyl)-1,2-ethanediamine (H(2)bbpen) and its derivatives as extractants. From the numerical analysis of the intricate extraction behavior of the metals, it was found that they were extracted into chloroform not only as uncharged chelate complexes but also as ion-pairs of charged complexes with a counter anion in aqueous solution. In other words, these ligands seemed to act not only as divalent hexadentate extractants but also as monovalent tri- or tetra dentate ligands, forming positively charged complexes. Furthermore, the order of the extractabilities between the metals did not coincide with the Irving-Williams series of stability because of the 'cavity size' in the ligands and the structural rigidity of them.     

癸二酸二水杨酰肼的合成

分别以水杨酰肼和癸二酰氯,或水杨酰氯和癸二酸二酰肼为原料合成了癸二酸二水杨酰肼(5),其结构经1H NMR, 13C NMR, MS和元素分析表征.合成5的较适宜反应条件为:癸二酰氯13 mmol, n(水杨酰肼) ∶ n(癸二酰氯)=2.2 ∶ 1.0,三乙胺作缚酸剂,DMF作溶剂,于90 ℃反应7 h,收率80%.     

Infrared spectra of seeded hydrogen clusters: (paraH2)N - OCS, (orthoH2)N - OCS, and (HD)N - OCS, N = 2 - 7

Infrared spectra of hydrogen-carbonyl sulfide clusters containing paraH2, orthoH2, or HD have been studied in the 2060 cm(-1) region of the C-O stretching vibration. The clusters were formed in pulsed supersonic jet expansions and probed using a tunable infrared diode laser spectrometer. Simple symmetric rotor type spectra were observed and assigned for clusters containing up to N = 7 hydrogen molecules. There was no resolved K structure, and Q-branch features were present for orthoH2 and HD but absent for paraH2. These characteristics can be rationalized in terms of near symmetric rotor structures, very low effective rotational temperatures (0.15 to 0.6 K), and nuclear spin statistics. The observed vibrational shifts were compared with those from recent observations on the same clusters embedded in helium nanodroplets. The observed rotational constants for the paraH2 clusters are in good agreement with a recent quantum Monte Carlo simulation. Some mixed clusters were also observed, such as HD-HD-He-OCS and paraH2 - orthoH2 - OCS.