Martin Klessinger

Bio: Martin Klessinger is an academic researcher from University of Göttingen. The author has contributed to research in topics: Bond order & Bond length. The author has an hindex of 6, co-authored 8 publications receiving 220 citations.

Theoretische und spektroskopische Untersuchungen an Indigofarbstoffen, I. Infrarot‐ und Lichtabsorptionsspektren einfacher Indigofarbstoffe

Abstract: Die vCo-Banden der IR-Spektren und die Lichtabsorption einiger Indigoide werden im Zusammenhang mit der Ladungsverteilung im molekularen π-Elektronensystem diskutiert. Dabei werden besonders der Einflus der Oxydationsstufe und der Abwandlung des Funfring-Heteroatoms sowie die Natur der Wasserstoffbrucken erortert.

Theoretische und spektroskopische Untersuchungen an Indigofarbstoffen, III. Der Einfluß zwischenmolekularer Wasserstoffbrücken auf die Spektren von Indigo im festen Zustand

Abstract: Die Frequenz der CO-Valenzschwingung des Indigodampfes wurde mit einer bis 400° heizbaren Kuvette zu 1662/cm bestimmt; ihre starke Verschiebung gegenuber ihrer Lage im kristallisierten Zustand (νCO = 1626/cm) wird auf zwischenmolekulare Wasserstoffbrucken zuruckgefuhrt, deren Einflus auf die IR- und Elektronen-Spektren des Indigos in HMO-Rechnungen durch eine Variation der Coulomb-Integrale der Ringheteroatome wiedergegeben werden kann.

Pariser-Parr-Pople-Rechnungen an Molekülen mit Aminogruppen

Abstract: Die Ergebnisse von PPP-Rechnungen fur Cyanine, Merocyanine und Aminochinone stehen in guter Ubereinstimmung mit den experimentellen Elektronen- und Schwingungsspektren. Das Spektrum des 2,5-Diaminobenzochinons-1,4 mus als unter Substituenteneinflus langwellig verschobenes p-Benzochinonspektrum gedeutet werden. Auch die Ladungsverteilung dieses Diaminochinons unterscheidet sich nur sehr wenig von derjenigen des Chinons. Diese Ergebnisse stutzen die Zuordnung der IR-Spektren der Aminochinone von Draber und Wallenfels und zeigen, das in den Aminochinonen der Chinoncharakter so ausgepragt ist, das es unnotig erscheint, sie als Quadrupol-merocyanine zu formulieren.

Gaussian expansions of minimal STO basis for calculations in molecular quantum mechanics

Abstract: By means of minimal basis SCF calculations for HF, H2O, NH3 and CH4 different expansions of Slater orbitals (STO) in terms of Gaussian orbitals (GTO) are tested in order to find an appropriate compromise between sufficient accuracy of the results and reasonable computing times. The least squares fit of the GTO expansion to STO does not appear to have any advantages over the expansion based on a variational procedure. It turns out that for hydrogens an expansion of the 1s orbital in terms of three GTO is quite sufficient, whereas for first row atoms an expansion of the 1s orbital in terms of three to five GTO, of the 2s orbital in terms of two GTO and of the 2p orbitals in terms of three GTO seems to be adequate.

TD-DFT Performance for the Visible Absorption Spectra of Organic Dyes: Conventional versus Long-Range Hybrids

Abstract: The π → π* transitions of more than 100 organic dyes from the major classes of chromophores (quinones, diazo, ...) have been investigated using a Time-Dependent Density Functional Theory (TD-DFT) procedure relying on large atomic basis sets and the systematic modeling of solvent effects. These calculations have been performed with pure (PBE) as well as conventional (PBE0) and long-range (LR) corrected hybrid functionals (LC-PBE, LC-ωPBE, and CAM-B3LYP). The computed wavelengths are systematically guided by the percentage of exact exchange included at intermediate interelectronic distance, i.e., the λmax value always follows the PBE > PBE0 > CAM-B3LYP > LC-PBE > LC-ωPBE > HF sequence. The functional giving the best estimates of the experimental transition energies may vary, but PBE0 and CAM-B3LYP tend to outperform all other approaches. The latter functional is shown to be especially adequate to treat molecules with delocalized excited states. The mean absolute error provided by PBE0 is 22 nm (0.14 eV) wit...

Indigo - a natural pigment for high performance ambipolar organic field effect transistors and circuits

Abstract: strong intermolecular interactions and with reversible reduction and oxidation reactions characterized by means of optical, electrical, and morphological investigations on thin indigo fi lms. The OFETs and complementary-like inverters are among the best reported organic devices to date, in terms of mobility, voltage gain, symmetry, p- and n-type channel balance, low operating voltage window and high ON/OFF ratio. Moreover, these devices show that high performance electronics can be fabricated entirely from non-toxic, biodegradable, and extremely cheap materials.

Dye chemistry with time-dependent density functional theory

Abstract: In this perspective, we present an overview of the determination of excited-state properties of "real-life" dyes, and notably of their optical absorption and emission spectra, performed during the last decade with time-dependent density functional theory (TD-DFT). We discuss the results obtained with both vertical and adiabatic (vibronic) approximations, choosing relevant examples for several series of dyes. These examples include reproducing absorption wavelengths of numerous families of coloured molecules, understanding the specific band shape of amino-anthraquinones, optimising the properties of dyes used in solar cells, mimicking the fluorescence wavelengths of fluorescent brighteners and BODIPY dyes, studying optically active biomolecules and photo-induced proton transfer, as well as improving the properties of photochromes.

Thioindigo dyes: highly accurate visible spectra with TD-DFT.

Abstract: The structure and visible spectra of a large panel of thioindigo dyes and derivatives have been evaluated using a TD-PBE0/6-311+G(2d,p)//PBE0/6-311G(d,p) approach explicitly taking bulk solvent effects into account by means of the polarizable continuum model. The influence of the solvent characteristics, the trans−cis isomerization, and the chemical substitution on the benzene rings have been investigated. In addition, hemi-thioindigo dyes, thiazine-indigo, chromophore-like molecules, and selenoindigo have been considered. Though the relative oscillator strengths of the two allowed visible transitions in the nonplanar cis isomers are not always correctly reproduced by theory, the agreement between theoretical and experimental results is far above expectations. For the 170 cases studied, we obtained a mean unsigned error on the predicted λmax limited to 6.9 nm or 0.03 eV, with only 6 (4) cases for which the difference exceeds 20 nm (0.10 eV). These errors are 1 order of magnitude smaller than what has prev...

Tyrian Purple: 6,6’-Dibromoindigo and Related Compounds

Abstract: The genesis of the purple dye from shellfish, its composition, origin,intermediates, analysis and synthesis of the components, 6,6’-dibromoindigo, 6-bromoindigo and 6,6’-dibromoindirubin are reviewed Keywords: 6,6’-dibromoindigo, 6-bromoindigo, 6,6’-dibromoindirubin, tyrindoxyl,tyriverdin, tyrindoleninone, tyrindolinone, synthesis, structure, properties Introduction 6,6’-Dibromoindigo is a major component of the historic pigment Tyrian purple, also known asRoyal purple, shellfish purple and Purple of the Ancients. Arguably, it is the oldest known pigment,the longest lasting, the subject of the first chemical industry, the most expensive and the best known.The colour is derived exclusively from marine shellfish of the Muricidae and Thaisidae families. Thelong history, stretching back well into the pre-chemical era, and embracing chemistry, biology andsociology, contains not a few misconceptions and erroneous conclusions. This review attempts to setthe record straight.This molluscan dye has been known since pre-Roman times and in the Mediterranean region thereis evidence for the industry around the 13th century B.C. [1] at Sarepta, now Sarafand, Lebanon. Theancient industry was distributed world-wide [2]. Surviving details of the ancient process areinsufficient to explain the chemistry involved and this is the subject of continuing speculation. But it isclear that the dye does not exist in the mollusc and is generated from precursors, sometimes termed