Electronic spectra of phenyl-, 3-pyridyl-, furfuryl-, and 2-theinyl-imino derivatives of thiazole: Molecular orbital treatment

The electronic spectra of phenylmethylene, 3-pyridylmethylene, furfurylmethylene, and theinylmethylene derivatives of 2-aminothiazole have been investigated. Gaussian analysis for the spectra indicates the existence of four electronic transitions in the 350–220 nm region. Geometry optimization using AM1 method followed by INDO/S-CI calculations was carried out. The results confirmed the absence of n–π* transitions. The coefficients of configuration interaction (CI) wave functions defined the type of electronic transitions, which are of major charge transfer (CT) character. The anticonformer is the predominant one. The gap energies of the studied compounds are of the same order, which indicates that their reactivities are expected to be the same. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66 : 415–423, 1998     

Theoretical Investigation on Electronic Transition of Tris(8-quinolinolate) Aluminum Grafted on Poly(p-phenylenevinylene) Units with the Localized-density-matrix Method

An unsystematic molecule PPV‐Alq₃ [3‐(4‐((E)‐2‐(8‐hydroxy‐3‐(4‐styrylstyryl)quinolin‐Alq₂‐6‐yl)vinyl)‐ styryl)‐6‐(4‐styrylstyryl)quinolin‐8‐olate‐Alq₂; q=8‐quinolinolate], which combines poly(p‐phenylenevinylene) with tris(8‐quinolinolate)aluminum, has been studied using a localized‐density‐matrix method. The absorption spectra and electronic transition properties were analyzed and compared with both intermediate neglect of the differential overlap method and the localized‐density‐matrix method. Great efforts have been made on investigating conjugated system on the absorption properties as these can be particularly important for many applications. Two different absorptions of the special molecule, tris(8‐quinolinolate)aluminum grafted on poly(p‐phenylenevinylene) units, were further discussed with density matrices. For the molecule, the first absorption peak is at 413 nm near the purple light. Two 8‐hydroxyquinolines have very slight electronic transition properties. Another absorption peak is at 237 nm. The second characteristic peak of molecule is completely different from that of the first one, which comes from contribution of 8‐hyroxyquinolines in the two different side chains. Our studies show that electronic transition properties of poly(p‐phenylenevinylene) can be effectively tuned by grafting tris(8‐quinolinolate)‐aluminum on poly(p‐phenylenevinylene) from the standpoint of transition energies, frontier molecular orbitals and density matrices.     

Time Resolved Spectroscopy of a Pulsed Discharge Through Water Vapor: Observation of Emissions from the C2σ+ State of OH

the (0–9) C²σ⁺ - A²σ⁺ band of OH and a complex emission located around 1850 Å are both observed as a function of time in a pulsed discharge through water vapor. The results are discussed in the light of Felenbok's interpretation of the origin of the 1850 Å emission.     

Dicyanmethylenpyrazolinone und deren Bedeutung als Chromophor. Synthesen mit Nitrilen, 80. Mitt.

1-Phenyl-2-pyrazolin-5-ones1 a–e react with tetracyanoethylene forming the corresponding dicyanomethylenepyrazolin-5-ones2 a–e. The products are deeply coloured with absorption bands between 550 and 650 nm, but low -values and negative solvatochromic effect. By amine-HCN exchange reaction with anilines the red-coloured phenylamino-cyanomethylene-pyrazolinones3–6 are obtained.¹⁵N- and¹³C-NMR-data of2 and quantum-chemical calculations (INDO/S-CI) reveal the extreme polarization and chromophoric properties of the described dicyanomethylene-pyrazolinones.

     

Nonrigid molecular behaviour of beryllium borohydride I. INDO study

Potential barriers of internal motions in three different structures of beryllium borohydride have been calculated by the INDO method. INDO results show that only two structures can be optimised along the path of interconversion.     

An intermediate neglect of differential overlap technique for spectroscopy: Pyrrole and the azines

An LCAO-MO-SCF-CI model along the lines introduced by Del Bene and Jaffé is developed that is capable of reproducing the better identified observed spectra of nitrogen heterocycles with a rms error of 1000 cm^–1. The model is applied to the spectra of pyrrole, benzene, pyridine, the diazines, symmetric triazine and symmetric tetrazine. The benzene and pyridine spectra are reproduced nearly exactly. The band observed in pyrrole at 6.5 eV is calculated as two bands at 6.5 eV, but they are assigned ^* and not . No evidence is found for the low lying ¹ B _2g in pyrazine, reported at 30400 cm^–1 in pure crystals. The lowest excited singlet of sym. triazine is calculated as ¹ E (n ^*), not ¹ A2 (n), in agreement with a recent interpretation of Fischer and Small. Several bands are reassigned, and the electronic nature of the transitions discussed. Naphthalene and quinoxaline are examined to insure that no large drift of results are met with molecules of other sizes. Comparison of eigenvalues with molecular ionization potentials is made. Here the numerical agreement appears satisfactory for the first few ionization potentials only.     

双核金属酞菁类化合物催化脱硫机理研究V──MPc─PcM与分子O_2的键合及荷移方式

结合光谱测定和量子化学理论计算（ＩＮＤＯ／Ｓ）结果探讨了在双核金属酞菁类化合物催化下以Ｏ_２作氧源的氧化─还原反应中，分子Ｏ_２与催化剂分子的键合及荷移方式．循环伏安测定表明催化反应过程中Ｏ_２与催化剂分子结合，且被活化；ＥＳＲ及ＩＲ光谱显示Ｏ_２被活化后的形式为；吸收光谱则表明催化剂在活化氧后其中心金属离子由Ｍ（Ⅱ）变为Ｍ（Ⅲ）．ＩＮＤＯ／Ｓ计算结果表明双核金属酞菁类化合物具有两种稳定结构Ｍ（Ⅱ）Ｐｃ──ＰｃＭ（Ⅱ）和Ｍ（Ⅰ）Ｐｃ──ＰｃＭ（Ⅲ），且后者相对更稳定．分子Ｏ_２与催化剂分子的键合方式为端配位，就Ｍ─Ｏ键强度和对Ｏ_２分子活化性能的比较而言存在顺序：Ｏ_２─Ｍ（Ⅰ）Ｐｃ＞Ｏ_２─Ｍ（Ⅱ）Ｐｃ＞Ｏ_２─Ｍ（Ⅲ）Ｐｃ．     

7—氮吲哚二体激发态双质子转移的量子化学研究

用AMl和INDO/CI方法研究了7-氮吲哚二体激发态双质子转移反应的位能面和机理,异构二体虽存在较强的分子内氢键,但基态时正常二体的能量仍比异构二体低,光照时正常二体可通过激发态质子转移变为异构二体,这是其荧光产生反常Stokes位移的原因。     

C_（60）~＋的Jahn－Teller结构畸变

用ＩＮＤＯ系列方法对Ｃ_（６０）的阳离子自由基Ｃ_（６０）~＋进行几何构型优化，得到Ｄ_（５ｄ）对称性的构型，表明Ｃ_（６０）~＋确实发生了Ｊａｈｎ－Ｔｅｌｌｅｒ结构畸变，形成７种键和４种不等同Ｃ原子，且单键变短，双键变长，键长趋于平均化，体系的正电荷和单电子主要分布在赤道附近，从而导致了赤道附近Ｃ原子的高反应活性。     

Electronic structures and spectra for triepoxides of fullerene C78O3

The equilibrium structures and relative stabilities of the possible 21 lower‐energy isomers for C₇₈O₃ based on C₇₈ (C_2v) were studied by intermediate neglect of differential overlap (INDO) calculations. It was indicated that the most stable geometry is 28,29,30,31,52,53‐C₇₈O₃, where three oxygen atoms are added to the same hexagon passed by the longest axis of C₇₈ (C_2v) and epoxide structures are formed. Electronic spectra of C₇₈O₃ isomers were investigated based on the optimized geometries. The blue shift of the absorptions for 28,29,30,31,52,53‐C₇₈O₃ compared with that of C₇₈ (C_2v) was rationalized and nature of transition of the peaks discussed. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005