新型水溶性萘啶基荧光材料的制备及性能研究

本文制备得到一种新型萘啶基的水溶性光致发光聚合物:聚丙烯酸(PAA)-2-苄氨基-7-甲基-1,8-萘啶,PAA₅-PAMN₂(PAMN是2-phenmethy-lamino-7-methyl-1,8-naphthyridine的缩写),经光谱分析和密度泛函理论计算,研究了化合物的结构和组成.这种聚合物在酸性和碱性条件下呈现最大的吸收波长分别为364和342 nm.Zn(OAc)₂的加入致使PAA₅-PAMN₂水溶液的荧光猝灭,而当OAc^-改变为NO₃^-时,在荧光强度不断降低的同时,由于NO₃^-离子的配位使最大发射波长从410 nm蓝移到400 nm.Na⁺+离子对其没有明显的荧光猝灭效应.     

在十二烷基硫酸钠存在下,用新显色剂DMTAE分光光度法测定矿样中钴

在十二烷基硫酸钠(SLS)存在下,钴与新显色剂2-(4,5-二甲基-2噻唑偶氮)-5-二乙胺基酚(DMTAE)在氨性溶液中形成1:2络合物。络合物最大吸收波长为592nm;摩尔吸光系数为6.14×10~4。它可被盐酸酸化,溶液酸度可达3mol/L。酸化以后,络合物组成比仍为1:2;最大吸收波长红移到614nm;摩尔吸光系数为4.52×10~4。经过酸化,其他金属络合物被破坏。在酸化条件下,对矿样中的钴进行了测定,结果较好。     

聚合位点对齐聚乙烯基噻吩光谱的影响

利用密度泛函理论PBE0方法,在6-31G基组水平上,对12种采用不同聚合位点的乙烯基噻吩二聚体分子进行了全优化,得到分子的紫外-可见吸收光谱.探讨了聚合位点对齐聚乙烯基噻吩吸收光谱、电子亲和势、电离能和重组能的影响,并研究了聚合度对乙烯基噻吩齐聚物吸收光谱的影响.计算结果表明:采用邻位聚合的乙烯基噻吩二聚体的能隙最小,电离能EIP最小,电子亲和势EEA最高,最大吸收波长较大,吸收强度大,λmax=377.33nm,f=1.0242.随着聚合度的增加,齐聚乙烯基噻吩的吸收光谱发生红移,吸收峰变宽,吸光度增大.十六聚体的最大吸收范围为500~1200nm,最大吸收波长为801.28nm时吸收值为7.003×105L·mol~(-1)·cm~(-1).     

1-(4-硝基苯基)-3-(5-溴吡啶)-三氮烯的合成及其与镉(Ⅱ)离子的显色反应

报道了 1 (4 硝基苯基) 3 (5 溴吡啶)三氮烯(NPBPDT)的合成及其与镉的显色反应.在TritonX 100的存在下,该试剂能与镉发生显色反应,形成摩尔比为 2∶1型的黄色配合物,在 440nm处有一最大正吸收峰,在540nm处有一最大负吸收峰.以 440nm为参比波长, 540nm为测量波长进行双波长测定,表观摩尔吸光系数为3. 14×105 L·mol-1·cm-1,镉的浓度在 0~0. 48mg/L范围内遵守比尔定律.用拟定方法测定废水中的微量镉,结果满意.     

新显色剂NPHMPDT的合成及其与镉的显色反应

报道了1-(4-硝基苯基)-3-(4-羟基-6甲基-嘧啶)-三氮烯(NPHMPDT)的合成及其与镉的显色反应研究.在表面活性剂OP存在下,pH 11.0的Na2B4O7-NaOH缓冲溶液中,该试剂能与镉发生显色反应,镉与NPHMPDT形成摩尔比为1:3型的淡黄色配合物,在450 nm处有一最大正吸收,在540 nm处有一最大负吸收.以450 nm为参比波长,540 nm为测量波长进行双波长测定,表观摩尔吸光系数为4.88×105 L·mol-1·cm-1,镉的质量浓度在0～480 μg/L范围内符合比尔定律.     

1-(4-硝基苯基)-3-(3,5-二溴吡啶)三氮烯的合成及其与汞的显色反应

合成了1-(4-硝基苯基)-3-(3,5-二溴吡啶)三氮烯(NPDBPDT),并研究了NPDBPDT与汞的显色反应.在Na2B4O7-NaOH缓冲溶液(pH11.0)介质中,在Triton X-100存在下Hg(Ⅱ)与试剂生成络合物(1∶2).络合物在450 nm处有最大正吸收峰,表观摩尔吸光系数为1.36×105 L·mol-1·cm-1,在535 nm处有最大负吸收峰,表观摩尔吸光系数为1.57×105 L·mol-1·cm-1,以535 nm为参比波长,以450 nm为测量波长进行双波长测定,表观摩尔吸光系数为2.93×105 L·mol-1·cm-1.汞量在0～0.48 μg/mL范围内符合比耳定律.     

头孢噻肟钠与茜素的显色反应及其分析应用

在pH6.5～8.7的条件下,头孢噻肟钠(CEFS)与茜素(ALZ)反应生成具有正吸收峰和负吸收峰的玫瑰红色络合物,最大正吸收波长位于538nm,最大负吸收波长位于446nm,表观摩尔吸光系数(ε)分别为2.33×104L.mol-1.cm-1(正吸收)和1.78×104L.mol-1.cm-1(负吸收),线性范围为0.2～9.2mg/L(正吸收)和0.2～8.2mg/L(负吸收)。当用正负光吸收叠加时,灵敏度更高。头孢噻肟钠在一定浓度范围内遵从朗伯-比尔定律,由此建立了测定头孢噻肟钠的光度分析法,并探讨了适宜的反应条件、主要分析化学性质及络合比。该法用于市售头孢噻肟钠药物含量的测定,结果满意。     

新显色剂1-(4-硝基苯基)-3-(5-氯吡啶)三氮烯的合成及其与镉的显色反应

报道了1-(4-硝基苯基)-3-(5-氯吡啶)三氮烯(NPCPDT)的合成及其与镉的显色反应研究。在Triton X-100的存在下,pH 11.5的Na2B4O7-NaOH缓冲溶液中,该试剂能与镉发生显色反应,镉与NPCPDT形成摩尔比为1∶3的黄色配合物,在440 nm处有一最大吸收,在535 nm处有一最大负吸收。以440 nm为参比波长,535 nm为测量波长进行双波长测定,表观摩尔吸光系数为2.68×105L.mol-1.cm-1,镉的质量浓度在0~0.48μg/mL范围内符合比尔定律。用拟定方法测定废水和环境水样中的微量镉。     

1-(4-硝基苯)-3-(3-甲基吡啶)-三氮烯合成及其与铜的显色反应

报道了新显色剂 1-(4-硝基苯)-3-(3-甲基吡啶)-三氮烯(NPMPDT)的合成及其与铜的显色反应.在OP的存在下,pH 10.5的Na2B4O7-NaOH缓冲溶液中,该试剂能与铜发生显色反应,铜与NPMPDT形成摩尔比为2∶1型的黄色配合物,在460 nm处有一最大正吸收,在535 nm 处有一最大负吸收.以460 nm为参比波长,535 nm为测量波长进行双波长测定,其表观摩尔吸光系数ε＝2.18×105 L·mol-1·cm-1,铜的质量浓度在0～0.48 μg/mL 范围内符合比尔定律,用本法测定大米和面粉中微量的铜,结果满意.     

2-苯基吡啶铱(Ⅲ)配合物及其衍生物光谱性质的理论研究

采用密度泛函理论B3PW91和UB3PW91方法, 分别对4种Ir(Ⅲ)配合物(ppy)₂Ir(acac)(1, ppy=2-苯基吡啶, acac=乙酰丙酮)、(npy)₂Ir(acac)(2, npy=2-萘-1-基吡啶)、(pq)₂Ir(acac)(3, pq=2-苯基喹啉)和(bzq)₂Ir(acac)(4, bzq=苯并喹啉)进行了基态和激发态的几何优化, 在此基础上用TD-DFT方法计算了吸收和发射光谱. 结果表明, 随着ppy配体上并苯环位置的变化, 参与最大吸收和发射的分子轨道能隙降低程度不同, 从而使配合物2, 3, 4的最大吸收和发射光谱都比配合物1发生红移, 其中在吡啶环上增加苯环对吸收光谱的影响最大. 这4个分子最大吸收波长的顺序为1<2<4<3, 而最大发射波长顺序则是1<4<3<2. 由于配合物2的两个苯环上H的强排斥作用降低了其共轭程度, 使分子发生很大程度的扭曲, 导致其斯托克位移最大.     

Ab initio study of the electronic spectrum of peroxyacetyl nitrate

A theoretical study of the ground and excited states of peroxyacetyl nitrate (PAN), CH3C(O)OONO2, has been carried out using high level ab initio molecular orbital methods. The ground state geometry and vibrational frequencies are calculated using the coupled-cluster method. The vertical excitation energies for the lowest three excited states are calculated using the complete active space self-consistent field method along with the multireference internally contracted configuration interaction method. These results are compared with vertical excitation energies calculated with the coupled cluster equation of motion method. The calculation provides relevant insight into the origin of PAN absorption in the UV wavelength region from 200 to 300 nm. The nature of the electron transitions for these excited states is discussed.     

N-丙烯酰吩噻嗪异构体的量子化学研究

用量子化学从头算方法 ,在RHF/ 6_31G 的水平上 ,对N_丙烯酰吩噻嗪分子两种异构体进行了理论计算 ,优化得到了它们的平衡几何构型 ,并计算了它们的谐振动频率 .结果表明 :N_丙烯酰吩噻嗪分子两种异构体的稳定性不同 .用PM3/CIS和AM1/CIS方法计算了它们的电子光谱 ,得到了由基态到各激发态的垂直跃迁能和相应的振子强度 .这些结果对探讨N_丙烯酰吩噻嗪引发丙烯腈聚合的机理是有益的     

On the ultraviolet photodissociation of H(2)Te

The photodissociation of H(2)Te through excitation in the first absorption band is investigated by means of multireference spin-orbit configuration interaction (CI) calculations. Bending potentials for low-lying electronic states of H(2)Te are obtained in C(2v) symmetry for Te-H distances fixed at the ground state equilibrium value of 3.14a(0), as well as for the minimum energy path constrained to R(1)=R(2). Asymmetric cuts of potential energy surfaces for excited states (at R(1)=3.14a(0) and theta;=90.3 degrees ) are obtained for the first time. It is shown that vibrational structure in the 380-400 nm region of the long wavelength absorption tail is due to transitions to 3A('), which has a shallow minimum at large HTe-H separations. Transitions to this state are polarized in the molecular plane, and this state converges to the excited TeH((2)Pi(1/2))+H((2)S) limit. These theoretical data are in accord with the selectivity toward TeH((2)Pi(1/2)) relative to TeH((2)Pi(3/2)) that has been found experimentally for 355 nm H(2)Te photodissociation. The calculated 3A(')<--XA(') transition dipole moment increases rapidly with HTe-H distance; this explains the observation of 3A(') vibrational structure for low vibrational levels, despite unfavorable Franck-Condon factors. According to the calculated vertical energies and transition moment data, the maximum in the first absorption band at approximately 245 nm is caused by excitation to 4A("), which has predominantly 2(1)A(") ((1)B(1) in C(2v) symmetry) character.     

The electronic spectrum and photodissociation of dinitrogen tetroxide (N(2)O(4)): Multireference configuration interaction studies

Multireference configuration interaction (MRCI) calculations were performed for vertical excitation energies and potential curves of N(2)O(4) in D(2h) symmetry using the TZVPP basis set with diffuse functions on the nitrogens. The strong absorption of N(2)O(4) around 185 nm is assigned to the transition from the ground state to 1?(1)B(1u) (σ(O)→σ(?) (N-N)) rather than 1?(1)B(2u) (π(O)→π(?) (NO(2) ),n→σ(?) (N-N)), as previously assumed. (N(2)O(4) is placed in the yz-plane, with N-N along z.) Transition to 1?(1)B(1u) is calculated to have an oscillator strength f=0.71 and is z-polarized, in agreement with the experimental observations. Another state, 2?(1)B(2u), lies close by, however, at a much lower f-value. The weak absorption around 340 nm is assigned to 1?(1)B(3u). Excitation to 1?(1)B(2u) is calculated at 227 nm. There is no clear assignment of a state for the observed shoulder around 260 nm. TD-DFT (time-dependent density functional theory) vertical excitation energies are close to MRCI values. MRCI singlet and triplet potential curves for the dissociation N(2)O(4)→2NO(2), combined with a table of NO(2) states correlating with those of N(2)O(4), indicate possible products of photodissociation at various wavelengths. The extensive literature on the photodissociation of N(2)O(4) is reviewed. DFT geometry optimizations have been performed on low-lying singlet and triplet states.     

Theoretical study of the singlet electronically excited states of N4

Vertical excitation energies for the lowest eleven singlet states of T_d N₄ were calculated using the TD-DFT method with the B3LYP functional, and at the EOM-CCSD level of theory. The vertical excitation energies for the five lowest-lying excited states were also obtained using the state-averaged CASSCF, CASPT2, CASPT3, and MRCI + Q methods. Our results show that the five lowest-lying states are of valence character. EOM-CCSD/d-aug-cc-pVTZ calculations predict that there are two weakly allowed optical transitions of T₂ symmetry at 10.44 and 10.82 eV. The transition to the third T₂ state, which is predicted to be at 10.89 eV, has an oscillator strength about one order of magnitude higher.     

Ab initio study of the spectroscopy of CH3N and CH3CH2N

Complete active space (CAS) calculations with 6-311++g(3df,3pd) basis sets were performed for a large number of electronic states of the nitrate free radical (CH3N/CH3CH2N) and their positive and negative ions. All calculated states are valence states, and their characters are discussed in detail. To investigate the Jahn-Teller effect on the CH3N radical, Cs symmetry was used for both CH3N and CH3CH2N in calculations. The results (CASPT2 adiabatic excitation energies and CASSI oscillator strengths) suggest that the calculated transitions of CH3N at 32172 and 32139 cm(-1) are attributed to the 2(3)A' ' --> 1(3)A' ' and 1(3)A' --> 1(3)A' ', respectively, which is in accordance with the A3E --> X3A2 emission spectrum at T0 = 31 817 cm(-1). The calculated transitions of CH3CH2N at 334 nm are attributed to the 1(3)A' ' --> 2(3)A' ' and 1(3)A' ' --> 1(3)A', respectively, which is in accordance with the UV absorption spectrum of a series of 11 bands beginning at 335 nm. The vertical and adiabatic ionization energies were obtained to compare with the PES data. These results are in agreement with previous experimental data, which is discussed in detail.     

双核Au(Ⅰ)配合物[Y+]2[Au(i-mnt)]2(Y+=[n-Bu4N]+,K+,[Ph4As]+)发光机制的从头计算研究

用从头算方法研究[Au(i-mnt)]22-(i-mnt=i-marononitriledithiolate)的电子吸收和磷光发射性质,利用MP2和CIS方法分别优化了[Au(i-mnt)]22-基态和激发态几何结构.计算的基态Au(Ⅰ)—Au(Ⅰ)键长为0.2825nm,表明Au(Ⅰ)之间存在弱吸引作用.采用SCRF方法中IPCM模型模拟配合物在乙氰溶液中的行为,计算得到的最大吸收波长为315.5nm,指认X1Ag→A1Au来源于i-mnt配体内电荷转移跃迁.在436.2nm处得到具有B3Au→1Ag跃迁的磷光发射,指认为i-mnt配体内电荷转移和金属到配体电荷转移跃迁,与500nm乙氰溶液的发射相对应,为金属修饰的有机配体发光机制.     

Benchmarks of electronically excited states: basis set effects on CASPT2 results

Vertical excitation energies and one-electron properties are computed for the valence excited states of 28 medium-sized organic benchmark molecules using multistate multiconfigurational second-order perturbation theory (MS-CASPT2) and the augmented correlation-consistent aug-cc-pVTZ basis set. They are compared with previously reported MS-CASPT2 results obtained with the smaller TZVP basis. The basis set extension from TZVP to aug-cc-pVTZ causes rather minor and systematic shifts in the vertical excitation energies that are normally slightly reduced (on average by 0.11 eV for the singlets and by 0.09 eV for the triplets), whereas the changes in the calculated oscillator strengths and dipole moments are somewhat more pronounced on a relative scale. These basis set effects at the MS-CASPT2 level are qualitatively and quantitatively similar to those found at the coupled cluster level for the same set of benchmark molecules. The previously proposed theoretical best estimates (TBE-1) for the vertical excitation energies for 104 singlet and 63 triplet excited states of the benchmark molecules are upgraded by replacing TZVP with aug-cc-pVTZ data that yields a new reference set (TBE-2). Statistical evaluations of the performance of density functional theory (DFT) and semiempirical methods lead to the same ranking and very similar quantitative results for TBE-1 and TBE-2, with slightly better performance measures with respect to TBE-2. DFT/MRCI is most accurate among the investigated DFT-based approaches, while the OMx methods with orthogonalization corrections perform best at the semiempirical level.     

Femtosecond multiphoton ionization of pyrrole

The photoionization dynamics of pyrrole are investigated by using a photoelectron imaging method and a tunable femtosecond laser. Two-photon nonresonant ionization experiments in the wavelength range from 261 to 298 nm indicate that the cation and neutral ground states have similar structures. The main vibrational excitation in the cation ground state is the v(8) mode. Two-photon absorption at 406 nm projects neutral pyrrole into a mixed state comprising the 1B(2) valence and 3p Rydberg states. Ionization from this mixed state mainly results in the overtone excitation of vibrational mode v(8) and v(9) of the cation state. In the wavelength range from 336 to 364 nm, a mixed state comprising the 3d/4s Rydberg and the 4A(1) valence states are populated by the absorption of two photons through vibronic coupling. The partition ratio among these states varies with the excitation wavelength, resulting in dramatic changes in both kinetic energy distributions and angular distributions. As the laser wavelength becomes shorter, from 336 to 314 nm, higher excited states, 3B(2), 5A(1), 6A(1), 7B(1) and 4B(2), can be populated. Photoelectron angular distributions provide supplementary verification of assignments. Our experiments indicate that femtosecond multiphoton ionization and photoelectron imaging methods are powerful tools for investigating short-lived intermediated excited states, which cannot be detected in nanosecond experiments.     

Electronic structures of low-lying Bu excited states in trans-oligoenes: Pariser-Parr-Pople and ab initio calculations

Two lowest-lying excited singlets with B(u) symmetry of all-trans-oligoenes, the well-known ionic 1(1)B(u)(+) state as well as the "hidden" ionic-covalent-mixed 1(1)B(u)(-) state, are calculated within both the Pariser-Parr-Pople (PPP) model at full configuration interaction (FCI) level and ab initio methods. The vertical excitation energies as well as wavefunctions from PPP-FCI calculations are found to be in good agreement with those from high-level multi-reference methods, such as multi-reference complete active space self-consistent field (CASSCF) with second order perturbative corrections (CASPT2), multi-reference M?ller-Plesset perturbation theory (MRMP), and complete active space valence bond theory (CASVB). The oscillator strengths from PPP calculation are in good agreement with spectroscopy experiments. The relatively small oscillator strength of 1(1)B(u)(-) is due to the approximate electron-hole symmetry of this state. In addition, the bond lengths in both states are found to show remarkable relativity with the bond orders calculated with ground state geometries, which suggests a possible strategy for initial guess in geometry optimization of excited states.