Spectrofluorimetric determination of trace amount of coenzyme II using ciprofloxacin-terbium complex as a fluorescent probe

A new spectrofluorimetric method was developed for the determination of trace amount of nicotinamide adenine dinucleotide phosphate (NADP). Using terbium ion (Tb³⁺)-ciprofloxacin (CIP) complex as a fluorescent probe, in the buffer solution of pH=9.00, NADP can remarkably enhance the fluorescence intensity of the Tb³⁺-CIP complex at and the enhanced fluorescence intensity of Tb³⁺ ion is in proportion to the concentration of NADP. Optimum conditions for the determination of NADP were also investigated. The dynamic range for the determination of NADP is 4.9×10⁻⁷−3.7×10⁻⁶ mol L⁻¹ with detection limit of 1.3×10⁻⁷ mol L⁻¹. This method is simple, practical and relatively free interference from coexisting substances and can be successfully applied to determination of NADP in synthetic water samples. Moreover, the enhancement mechanisms of the fluorescence intensity in the Tb³⁺-CIP system and the Tb³⁺-CIP-NADP system have been also discussed.     

The v6 = 1 and v6 = 2 vibrational states of DCF3

The high-resolution infrared spectra of DCF₃ were reinvestigated in the ν₆ fundamental band region near 500 cm⁻¹ and around 1000 cm⁻¹ with the aim to assign and analyze the overtone level of the asymmetric CF₃ bending vibration v₆ = 2.The present paper reports on the first study of both its sublevels (A₁ and E corresponding to l = 0 and ±2, respectively) through the high-resolution analysis of the overtone band and the hot and bands.The well-known “loop method”, applied to and , yielded ground state energy differences Δ(K, J) = E₀(K, J) − E₀(K − 3,J) for the range of K = 6 to 30.In the final fitting of molecular parameters, we used the strategy of fitting all upper state data together with the ground state rotational transitions.This is equivalent to that calculating separately the and coefficients of the K-dependent part of the ground state energy terms from the combination loops.All rotational constants of the ground state up to sextic order could be refined in the calculation.This led to a very accurate determination of C₀ = 0.18924413(25) cm⁻¹, , and also .In the course of analyzing simultaneously the overtone band together with the and ν₆ bands, the original assignment of the fundamental ν₆ band [Bürger et al., J. Mol. Spectrosc. 182 (1997) 34-49] was found to be incompatible with the present one. Assignments of the (k + 1, l₆ = +1)/(k − 1,l₆ = −1) levels had to be interchanged, which changed the value of Cζ₆ = −0.14198768(26) cm⁻¹ and the sign of the combination of constants C − B − Cζ in the v₆ = 1 level to a negative value.     

A sensitive fluorimetric method for determination of trace amounts of nitrite based on luminescence energy transfer

An efficient luminescence energy transfer (LET) system based on terbium(III)-sodium hexametaphosphate (Tb/SHMP) chelates as donor and 4-((4-(2-aminoethylamino)naphthalen-1-yl)diazenyl)benzenesulfonic acid dihydrochloride (ANDBS) as acceptor was developed for sensitive determination of trace nitrite. Stable and strong fluorescence Tb/SHMP chelates were prepared in aqueous solution. Based on Griess Reaction, ANDBS was generated by the quantitative reaction of nitrite, sulfanilamide and N-(1-naphtyl)-ethylenediamine dihydrochloride (N1NED). The degree of the overlap was effective for LET between the emission spectrum of Tb/SHMP chelates and the absorption spectrum of ANDBS. Based on the luminescence intensity quenching of Tb/SHMP chelates in proportion to the trace amounts of nitrite, a new assay for the selective and sensitive determination of nitrite was developed. Under the optimum conditions, the linear calibration graph was obtained with a linear range of 0.00040-0.20 μg mL⁻¹ (R=0.99657). The detection limit of was 0.00010 μg mL⁻¹ (R=0.99657). The method was applied successfully to the determination of nitrite for synthetic samples.     

Fourier transform emission spectroscopy and ab initio calculations on NbCl

The emission spectrum of NbCl has been recorded in the 3000-20 000 cm⁻¹ region using a Fourier transform spectrometer. The bands were observed by microwave excitation of a mixture of NbCl₅ vapor and He. Two groups of bands observed in the 6500-7000 cm⁻¹ and 9800-11 000 cm⁻¹ regions have been assigned to two electronic transitions. Five bands observed in the 6500-7000 cm⁻¹ region consist of R, P, and Q branches with no combination defect or Λ-doubling. They have been assigned as five sub-bands of a ΔΛ=±1 transition with Λ>1. Nine bands observed in the 9800-11 000 cm⁻¹ regions consist of R and P branches, and they are also free from Λ-doubling. These bands have been classified into four sub-bands of a ΔΛ=0 transition (with Λ>1), which has tentatively been assigned as . The two transitions have no electronic states in common. Ab initio calculations have been performed on NbCl and the spectroscopic properties of the low-lying electronic states have been calculated. The ground state of NbCl has been predicted to be a state arising from the 3σ¹ 1δ² 2π¹ configuration, with a low-lying state at 1300 cm⁻¹ from the 3σ¹ 1δ¹ 2π² configuration. The results of our experimental and theoretical studies will be presented. This work represents the first experimental investigation of the spectra of NbCl and the first ab initio prediction of the spectroscopic properties of the low-lying electronic states.     

The formaldehyde cation: Rovibrational energy level structure and Coriolis interaction near the adiabatic ionization threshold

Rotationally resolved pulsed-field-ionization zero-kinetic-energy photoelectron spectra of the 0⁰, 6¹ and 4¹ vibrational levels of the ground electronic state of the formaldehyde cation were recorded using a resonant three-color three-photon excitation scheme. The first adiabatic ionization energy of CH₂O (87793.33(1.30) cm⁻¹) and the rigid-rotor rotational constants (A⁺ = 8.874(8) cm⁻¹, B⁺ = 1.342(15) cm⁻¹, C⁺ = 1.148(18) cm⁻¹) of the vibronic ground state of CH₂O⁺ were derived. A strong a-type Coriolis interaction between the 6¹ and 4¹ vibrational levels was observed. The Coriolis coupling parameter and the deperturbed fundamental vibrational frequencies of the in-plane-rocking mode ν₆ and the out-of-plane bending mode ν₄ were determined to be 8.70(10) cm⁻¹, 823.67(30) cm⁻¹ and 1036.50(30) cm⁻¹, respectively. The intensity distribution of the photoelectron spectra was analyzed in the realm of a simple photoionization model.     

Electronic absorption spectra of CCS and CCS in neon matrices

Mass selected C₂S⁻ ions have been co-deposited with neon to grow a matrix at 6 K. The and electronic absorption spectra of the linear CCS⁻ anion have been identified with origin band at 10 606 and 22 273 cm⁻¹, respectively. After exposure to UV radiation a new electronic transition of CCS is observed (origin band at 30 563 cm⁻¹) in addition to its known band system. Ab initio calculations provide support for the symmetry assignment of the upper electronic states of CCS⁻, CCS and of the vibrational structure in the spectra.     

Gas phase electronic spectrum of propadienylidene C3H2

The rotationally resolved vibronic bands in the forbidden electronic transition of the cumulene carbene C₃H₂ have been observed in the gas phase by cavity ring down absorption spectroscopy through a supersonic planar plasma with allene as precursor. The band detected in the 16 223 cm⁻¹ region is a result of vibronic interaction and is assigned to a combination of a₁ and b₂ vibrations with a frequency around 2250 cm⁻¹. Another vibronic band near 15 810 cm⁻¹ has an unusual rotational structure because the K_a = 0-1 subband is absent. It is assigned to a combination of a₁ and b₁ vibrations, ∼1850 cm⁻¹, which borrow intensity from the near lying state due to a-type Coriolis coupling. A rotational analysis using a conventional Hamiltonian for an asymmetric top molecule yields molecular constants for the vibrational excited levels of the ùA₂ state, which were used for the determination of the geometry. The stronger transition of C₃H₂, measured in a neon matrix in the 16 161-24 802 cm⁻¹ range, was not detected. The reason for this is a short lifetime of the state, leading to line broadening.     

The 2ν5 overtone bands of perchloryl fluoride

The high-resolution infrared spectra of the monoisotopic species F³⁵Cl¹⁶O₃, F³⁷Cl¹⁶O₃, F³⁵Cl¹⁸O₃ and F³⁷Cl¹⁸O₃ have been studied in the region of the 2ν₅ overtones, from 1100 to 1200 cm⁻¹. Both the parallel and the perpendicular components are clearly observed in the spectra, their origins differing by about 0.4 cm⁻¹. In each spectrum about 2000 transitions have been assigned, 35% of them belonging to . The parallel and perpendicular bands in each manifold have been analyzed separately since no evidence of perturbations has been observed. The rovibration parameters of the v₅ = 2, l₅ = 0 and v₅ = 2, l₅=?2 excited states have been obtained. For the four species combining the and band origins with those of the ν₅ fundamentals the harmonic wavenumbers, , and the x₅₅ and g₅₅ anharmonicity constants have also been derived.     

A visible spectrum of jet-cooled rhodium monosulfide

The diatomic molecule RhS has been observed for the first time. It has been studied by high resolution laser-induced fluorescence spectroscopy in a supersonic molecular beam following reaction by laser-vaporized rhodium atoms with CS₂ doped in He. Electronic, vibrational, and rotational data have been collected. The RhS ground state has ⁴Σ⁻ symmetry with a second-order spin-orbit splitting of 47.43 cm⁻¹, indicating case (a) coupling at low J. Three bands in the 535-555 nm region have been rotationally analyzed and give a bond length in the ground state of 0.2059 nm. A vibrational frequency ω_e ≈ 485 cm⁻¹ is estimated from dispersed fluorescence measurements.     

Spectroscopic characterization of the potential energy functions of Ne2 Rydberg states in the vicinity of the Ne(S0) + Ne(4p′) dissociation limits

The gerade autoionizing Rydberg states of Ne₂ have been studied in the range 162 000-172 000 cm⁻¹ by 1 + 1′ resonant two-photon excitation from the Ne₂ X ground state via different vibrational levels of the Ne₂ C state. A rotationally resolved part of the spectrum allowed the determination of the potential energy functions of two states of 1_g and characters in the vicinity of the Ne(2p⁶¹S₀) + Ne (2p⁵4p′) dissociation limit. The presence of maxima in these potential energy functions is interpreted as originating from a repulsive interaction between the Rydberg electron and the neutral atom.     

High-resolution FTIR and MMW study of the v4 = 2 (A1, E) excited state of NF3 near 985 cm: the axial ground state rotational constants derived by the “loop-method”

The two substates v₄ = 2⁰ (A₁, 983.702 cm⁻¹) and v₄ = 2^±2 (E, 986.622 cm⁻¹) of the oblate symmetric top molecule, ¹⁴NF₃, have been studied by high-resolution (2.5 × 10⁻³ cm⁻¹) infrared spectroscopy of the overtones and 2ν₄ − ν₄ hot bands. Transitions of the overtone, the hot band, and the previously measured fundamental band were combined to yield 585 ground state combination differences differing in K by ±3, with K_max = 36. Using the “loop-method,” a fit (standard deviation σ = 0.320 × 10⁻³ cm⁻¹) provided a complete set of the hitherto not experimentally known axial ground state constants. In units of cm⁻¹ these have the following values: . Upper state parameters were determined using a vibrationally isolated model. Considering l (2, 2) and l (2, −1) interactions between the v₄ = 2⁰ and v₄ = 2^±2 substates and effects accounting for the l (4, −2) interactions within the kl = −2 levels, 25 upper state parameters were obtained by fitting 2747 IR data (1842 transitions, 905 deduced energies, J_max = 42, K_max = 39) with σ_IR = 0.353 × 10⁻³ cm⁻¹. Moreover, millimeter-wave spectroscopy furnished 86 transitions (J_max = 16, K_max = 13) measured on the v₄ = 2 excited state. A merged fit, refining 24 parameters using the described model gave σ_IR = 0.365 × 10⁻³ cm⁻¹ andσ_MMW = 0.855 × 10⁻⁶ cm⁻¹ (26 kHz). The anharmonicity constants (in cm⁻¹) are x₄₄ = −0.84174 (2) and g₄₄ =  + 0.73014 (1). In addition to this model, the D, Q, and L reductions of the rovibrational Hamiltonian were tested. Standard deviations σ_IR = 0.375 × 10⁻³ cm⁻¹ and σ_MMW = 0.865 × 10⁻⁶ cm⁻¹ were obtained for both D and L reductions, and σ_IR = 0.392 × 10⁻³ cm⁻¹ and σ_MMW = 0.935 × 10⁻⁶ cm⁻¹ for Q reduction. The unitary equivalence of the majority of the 18 tested relations between the derived parameters was satisfactorily fulfilled. This confirms that the v₄ = 2 excited vibrational state can be considered in reasonable approximation to be isolated.     

High-resolution infrared and subterahertz spectroscopy of the v2 = 1, v5 = 1, and v3 = 2 levels of CH3Cl

High-resolution Fourier-transform infrared spectra between 1235 and 1680 cm⁻¹ and subterahertz spectra between 250 and 630 GHz of monoisotopic ¹³CH₃³⁵Cl have been recorded and analyzed simultaneously, with all Coriolis, α-resonance, and l-type interactions in the polyad of the v₂ = 1, v₅ = 1, and v₃ = 2 levels taken into account. Several α-resonances (Δk = ±2, Δl = ?1) generating perturbation-allowed transitions have been assigned in the rovibrational spectra. These resonances enabled us to determine accurately and independently the ground state rotational and centrifugal distortion parameters A₀ = 5.205 746 9 (55) cm⁻¹ and . Even , which is, however, correlated to higher-order α-resonance terms, was determined. With 51 upper state parameters varied, about 5800 rovibrational wavenumbers and more than 550 rotational frequencies pertaining to the excited vibrational states were fitted within their experimental accuracy.     

The 2ν4 overtone bands of FClO3

The high resolution infrared spectrum of the mono-isotopic species F³⁵Cl¹⁶O₃ has been studied in the region of the 2ν₄ overtone, from 2560 to 2680 cm⁻¹. The perpendicular component is strong and clearly observed while the parallel component is very weak and almost completely hidden by the perpendicular one. Their origins differ by 12.6 cm⁻¹, the being located at higher wavenumbers. The band is perturbed by the anharmonic interaction between the v₄ = 2, l₄ = ?2 and v₂ = v₄ = v₅ = 1, l₄ = l₅ = ±1 excited states, both of E symmetry. In total 3157 transitions have been assigned, 83% of these to , 12% to , and 5% to . The three bands have been analyzed simultaneously, taking into account the Fermi resonance effective between the excited states of E symmetry. The ro-vibration parameters of the excited states have been obtained, including the deperturbed band origins of and , at 2628.5890(4) and 2619.3342(5) cm⁻¹, respectively. The W₂₄₅ anharmonic constant is equal to 4.0161(4) cm⁻¹. The x₄₄+g₄₄ and x₂₄+x₄₅+g₄₅ anharmonicity constants have been derived from the obtained band origins and those of ν₄ and ν₂ + ν₅.     

Infrared emission spectroscopy of a new Σ-Σ system of TiCl

The spectra of TiCl have been reinvestigated in the 4200-8500 cm⁻¹ region using the 1-m Fourier transform spectrometer associated with the National Solar Observatory at Kitt Peak. The molecules were excited in a microwave discharge lamp operated with 3.0 Torr of He and a trace of TiCl₄ vapor, and the spectra were recorded at a resolution of 0.01 cm⁻¹. Three new bands with origins near 6938.9, 6900.2, and 6861.7 cm⁻¹ have been assigned as the 0-0, 1-1, and 2-2 bands of a new - transition. This assignment is supported by our recent ab initio calculations on TiCl and ZrCl [J. Chem. Phys. 114 (2001) 3977]. A rotational analysis of these bands has been carried out and spectroscopic constants have been extracted for the states.     

Laser excitation spectrum of C3 in the region 26 000-30 700 cm

The vibrational structure of the electronic state of C₃ in the region 26 000-30 775 cm⁻¹ has been re-examined, using laser excitation spectra of jet-cooled molecules. Rotational constants and vibrational energies have been determined for over 60 previously-unreported vibronic levels; a number of other levels have been re-assigned. The vibrational structure is complicated by interactions between levels of the upper and lower Born-Oppenheimer components of the state, and by the effects of the double minimum potential in the Q₃ coordinate, recognized by Izuha and Yamanouchi [16]. The present work shows that there is also strong anharmonic resonance between the overtones of the ν₁ and ν₃ vibrations. For instance, the levels 2 1⁺ 1 and 0 1 ⁺ 3 are nearly degenerate in zero order, but as a result of the resonance they give rise to two levels 139 cm⁻¹ apart, centered about the expected position of the 2 1⁺ 1 level. With these irregularities recognized, every observed vibrational level up to 30 000 cm⁻¹ (a vibrational energy of over 5000 cm⁻¹) can now be assigned. A vibronic level at 30181.4 cm⁻¹, which has a much lower B′ rotational constant than nearby levels of the state, possibly represents the onset of vibronic perturbations by the electronic state; this state is so far unknown, but is predicted by the ab initio calculations of Ahmed et al. [36].     

MRCI studies on the electronic structure of AlN and AlN, and the electron affinity of AlN

Using multireference configuration-interaction methods and double to triple-zeta basis sets with semidiffuse and polarization functions, potential energies and spectroscopic constants for low-lying doublet, and quartet states of AlN⁻ were calculated. has R_e=3.280 bohr and . lies 0.17 eV above the ground state. Using an estimated electron affinity of 2.1 eV for AlN, four states of AlN⁻ are found to be stable, namely , , , and . Comparisons with the isovalent anions BN⁻ (three stable states) and AlP⁻ (seven stable states) are made. Photo-detachment of an electron from the state of AlN⁻ can lead to an accurate determination of the energy difference between the two close-lying lowest states of AlN, and , predicted here to be 0.09 eV apart.     

Aromatic interactions in the close packing of phenyl-imides at Cu(1 1 0) surfaces

The oxidation of aniline at Cu(1 1 0) surfaces at 290 K has been studied by XPS and STM. A single chemisorbed product, assigned to a phenyl imide (C₆H₅N(a)), is formed together with water which desorbs. Reaction with preadsorbed oxygen results in a maximum surface concentration of phenyl imide of 2.8 × 10¹⁴ mol cm⁻² and a surface dominated by domains of three structures described by , and unit meshes. However, concentrations of phenyl imide of up to 3.3 × 10¹⁴ mol cm⁻² were obtained from the coadsorption of aniline and dioxygen (300:1 mixture) resulting in a highly ordered biphasic structure with and domains. Comparison of the STM and XPS data shows that only half the phenyl imides at the surface are imaged. Pi-stacking of the phenyl rings is proposed to account for this observation.     

The high-resolution infrared spectrum of BF3 from 400 to 1650 cm

High-resolution infrared spectra of boron trifluoride, enriched to 99.5 at. % ¹¹B, have been measured from 400 to 1650 cm⁻¹. In that region we have identified and analyzed 16 absorption bands attributed to the three fundamental bands, two combination bands, 10 hot bands, and one difference band. All possible states were accessed in this region through direct transitions either from the ground state or as hot bands from thermally populated levels. The spectral resolution of the measurements varied from 0.0015 to 0.0020 cm⁻¹. An improved set of ground state rotational constants and rovibrational constants for the infrared-active fundamental vibrations have been determined from over 32 000 assigned transitions. This study resulted in the first direct characterization of the infrared-inactive ν₁ state of ¹¹BF₃ leading to values for ν₁, , and of 885.843205(24), 0.000678548(53), and 0.000337564(66) cm⁻¹, respectively. The Fermi resonance perturbation between the E′ states ν₃ and 3ν₄ (l = ±1) was further elucidated by observation of hot band transitions to both the 3ν₄ (l = ±1) and 3ν₄ (l = ±3) states. Several other resonances were also found including the weak rotational interaction, between the state 2ν₂ and the E′ state of ν₁ + ν₄.