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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Syntéza pokročilých intermediátov na báze para-bis (2-thienyl) fenylenu so zabudovaným adamantanovým skeletom. Vplyv intramolekulárnych vodíkových väzieb na fotoizomerizáciu. / Synthesis of advanced adamantane containing intermediates based on para-bis (2-thienyl) phenylene. Influence of intramolecular hydrogen bonds on photoisomerization

Veselý, Dominik January 2021 (has links)
This diploma thesis describes study and onward synthesis of advanced organic structures with potential application in the field of organic electronics and, in particular, molecular photoswitches. In the theoretical part of the thesis are closely described most commonly used conventional molecular photoswitches with special attention to the influence of the structural modifications on properties and applications of the given derivatives. Next passage is dedicated to study of donor-acceptor systems, as fundamental building blocks for synthesis of advanced derivatives. The possibilities of derivatization with a goal of improving the physicochemical properties of these compounds are also discussed. In the final chapter are proposed modern synthetic methods for preparation of novel materials for organic electronics. This section is connected with an experimental part, where are designed and consequently synthesised 4 novel imine derivatives with dodecyl and adamantyl-ethyl side chain.
2

The synthesis, thermal and photochemical properties of cyclophanedienes and dihydropyrenes with different internal substituents

Ayub, Khurshid 12 December 2008 (has links)
A series of cyclophanedienes (CPDs) with different internal functional groups were synthesized. Dicyano CPD 85, cyano methyl CPD 127 and phenylethynyl/methyl CPD 138 were synthesized from bis-bromomethyl aromatics via a thiacyclophane- thiomethylcyclophane route. Diformyl cyclophanediene 152 and bis(hydroxymethyl) CPD 159 were obtained by the functional group transformation of CPDs 85 and 152 respectively. Cyclophanedienes with internal olefinic groups were obtained by three different routes: the best was the functional group transformations of the dicyano mercaptomethylcyclophane 99 followed by a Hoffmann elimination. Using the best synthetic route, CPDs with substituted vinyl groups such as alkylvinyl (162, 163, 178 and 198), butadienyl (184, 185 and 186), styryl (202, 203 and 204), nitro-substituted styryl (210, 211 and 212), methoxy-substituted styryl (218, 219 and 220) and methyl-substituted styryl (226, 227 and 228) were synthesized. Cyclophanediene 235 with an internal ethynyl (alkynyl) group was also synthesized by a similar synthetic route; however, it gave two major interesting side products; vinyl-ethynyl CPD 237 and vinyl-styryl CPD 240. The cyclophanedienes except dicyano 85, cyano-methyl 127 and diformyl 152 were converted to their corresponding dihydropyrenes both thermally and photochemically. Dicyano CPD 85 and cyano-methyl CPD 127 were converted photochemically to the DHPs 86 and 128, respectively. Diformyl CPD 152 underwent decomposition in any attempt to transform it into the DHP 154 either thermally or photochemically. Diphenylethynyl DHPs 141 and 247 were obtained by the Sonogashira coupling of diethynyl DHP 236. The Eglinton coupling reaction was used to achieve butadiynyl DHPs 257 and 254. Naphthoyl DHPs 248 and 250 were synthesized by the Friedel-Crafts acylation reaction of DHPs 179 and 167, respectively. All compounds were characterized by NMR, IR, and UV spectroscopy and mass spectrometry. Dicyano CPD 85 was quite stable towards thermal isomerization to the dihydropyrene 86 and showed a calculated half life of ~ 36 years (three orders of magnitude higher than that of benzo CPD 53 i.e., 7.3 days) at room temperature, whereas CPDs 127 (cyano methyl), 138 (phenylethynyl/methyl) and 152 (diformyl) showed half lives less than a month at 20 oC. Cyclophanedienes with internal ethynyl and substituted vinyl groups were quite stable thermally and showed half lives of several years (1-16 years) at room temperature. CPDs with cis substituted internal vinyl groups were thermally more stable than their trans counterparts. Electron withdrawing substituent (NO2) at the para positions of the internal styryl groups accelerate, whereas electron donating groups (MeO, Me) decelerate the thermal return reaction. Naphthoyl CPDs 249 and 251 isomerized at rates about 6-12 times faster than their non naphthoylated analogues 178 and 166 respectively. DHPs with internal ethenyl (167, 238 and 241), substituted ethynyl (139, 141 and 247) and trans substituted vinyl (199, 207, 215, 223 and 231) groups failed to open under visible light irradiation. Dicyano DHP 86, diethynyl DHP 236 and the unsymmetrical isomers of internal olefinic CPDs (206, 214, 222 and 230) formed photostationary states (pss). Disubstituted vinyl (179) and cis substituted vinyl DHPs (164, 205, 213, 221 and 229) opened completely; however their opening rates although faster than the parent 43, were 4-6 times slower than the benzo DHP 47. Introduction of an electron withdrawing substituent on the internal styryl group decelerated the visible opening reaction whereas electron donating groups accelerated it. 2-Naphthoyl divinyl DHP 250 opened at rates quite comparable to those of benzo DHP 47 whereas 2-naphthoyl diisobutenyl 248 opened about 25 times faster than the benzo DHP. The [1,5]-sigmatropic rearrangement of the internal nitrile (DHPs 86 and 128) and formyl (DHP 153) groups was observed. The sigmatropic rearrangement of the nitrile group in 86 was quite favorable in CDCl3 (Eact = 23.4 + 0.7 kcal/mol) compared to benzene (Eact = 28.6 + 1.2 kcal/mol). Formyl groups showed a much higher migration aptitude and Eact is estimated to be < 20 kcal/mol in any solvent. In this study, the best switch pair obtained was naphthoyl diisobutyl 248/249 which in comparison with previously the best switch pair 47/53 (benzo) showed much higher stability of the cyclophanediene (two orders of magnitude); moreover, the dihydropyrene opened about 25 times faster as well and is one of the best new photochromes yet.
3

Characterization of Azobenzene Derivatives with Respect to Photoswitching and Aggregation Properties

Day, Aaron M. January 2020 (has links)
No description available.
4

Photoschaltbare Katalysatoren

Peters, Maike Vivian 04 September 2008 (has links)
Ziel dieser Arbeit war die Kontrolle über bestimmte Eigenschaften von Molekülen. Dabei lag ein besonderes Interesse auf der Steuerung der Zugänglichkeit eines katalytisch aktiven Zentrums durch die großen geometrischen Veränderungen bei der E->Z Isomerie von photochromen Verbindungen. Ein weiterer Vorteil dieser photochromen Verbindungen liegt in der Reversibilität der E-Z Isomerisierung, so dass das katalytische Zentrum mehrmals „an“ und „aus“ geschaltet werden kann. In der Literatur sind nur sehr wenige Beispiele solcher photoschaltbaren Katalysatoren bekannt. Diese besitzen teilweise schwerwiegende Nachteile, wie z.B. geringe Reaktivitätsunterschiede oder eine begrenzte Anwendbarkeit, aufweisen. Die Aufgabe in dieser Arbeit bestand in der Entwicklung eines neuen photoschaltbaren Katalysatorsystems, welches sich durch größere Reaktivitätsunterschiede und eine breitere Anwendbarkeit auszeichnet. Das erste Design bestand aus einem photoschaltbaren Metalloporphyrin als Katalysator für Polymerisations- oder Oxidationsreaktionen. Nach erfolgreicher Synthese wurden die Schalteigenschaften untersucht. In einem zweiten Design wurde ein photoschaltbarer Organokatalysator hergestellt und dessen Schaltverhalten, sowie dessen Eignung als Katalysator in einer generellen Basenkatalyse, erfolgreich getestet. / The aim of this work was to control the properties of molecules. Our special interest lies in controlling the accessibility of a catalytic active center by using the big geometric changes of photochromic groups, such as E->Z isomerization of azobenzene or stilben. Another advantage of these photochromes is the reversibility of the Z -> E isomerization, so that the catalytic active center can be switched several times. Only few examples of photoswitchable catalysts are known in literature, having several disadvantages like small activity ratios or narrow scope. The goal of this work was to design a new photoswitchable catalyst having bigger activity ratios and broader applicability. The first design consisted of a photoswitchable metalloporphyrin as catalyst for polymerization or oxidation reactions. After successful synthesis the switching properties were investigated, showing no isomerization possibility. In a second approach a photoswitchable organo catalyst was established. The switching properties were investigated and the catalyst was successfully tested in general base catalysis.
5

Construction of Low‐Symmetric and Light-­Switchable Coordination Cages for Guest Uptake and Catalysis

Han, Muxin 08 October 2015 (has links)
No description available.
6

Curved Carbon Materials / Strained Macrocycles and Photomagnetic Switches

Grabicki, Niklas Jan 09 August 2023 (has links)
Das Ziel dieser Arbeit war die Synthese eindimensionaler Nanoröhren basierend auf leichten Elementen. Inspiriert von Kohlenstoff Nanoröhren werden Interessante Eigenschafte für diese Materialien erwartet. Aktuell ist die Synthese solcher Kohlenstoff Nanorohren nur mit vergleichsweise aufwendigen Methoden möglich. Hierbei stellt besonders die uniforme Synthese von Röhren mit exakt gleichen Durchmessern und Symmetrien ein noch ungelöstes Problem dar. Durch diese Arbeit erhofften wir uns eine völlig neue Arte der Synthese für solche 1D Nanomaterialien zu etablieren. Dazu wurden in Kapitel 2 und 3 zwei verschiedene Typen von gespannten aromatischen Makrozyklen synthetisiert. Die synthetisierten Makrozyklen zeichnen sich durch einen hohen Grad an Funktionalisierung aus, welcher zukünftig dazu genutzt werden soll die Prinzipien der dynamisch kovalenten Chemie in der finalen Materialsynthese anzuwenden. Der durch die Funktionalisierung erzeugte innere Hohlraum dieser zyklischen Verbindungen lässt sich nutzen, um verschiedene molekulare Gäste zu binden. Die Erkenntnisse in Bezug auf die Synthese solcher Makrozyklen, die hierbei erzielt wurden, werden entscheidend dazu beitragen, dass anfänglich beschriebene Ziel der nasschemischen Synthese 1D organischer Nanoröhren in Zukunft zu erreichen. Die Methoden, der Makrozyklisierung sollten in Kapitel 4 dazu genutzt werden einen chiralen aromatischen Makrozyklus auf Basis von [5]Helicen-Untereinheiten zu synthetisieren, allerdings ohne Erfolg. Stattdessen wurde ein Nebenprodukt isoliert, dass sich als bisher unbekannter molekulare Schalter erwies. Dieser Schalter erlaubt es durch Bestrahlung bei tiefen Temperaturen reversibel ein paramagnetisches Isomer zu erzeugen. Dadurch eröffnet sich eine völlig neue Klasse an molekularen Schaltern, deren Anwendungspotential den Rahmen dieser Arbeit überschreitet. / The aim of this work was the synthesis of one-dimensional nanotubes based on light elements. Inspired by carbon nanotubes, interesting properties for these materials are expected. Currently, the synthesis of such carbon nanotubes is only possible with comparatively complex methods. Especially the uniform synthesis of tubes with exactly the same diameters and symmetries is still an unsolved problem. Through this work we hoped to establish a completely new way of synthesis for such 1D nanomaterials. To this end, two different types of strained aromatic macrocycles were synthesized in Chapters 2 and 3. The synthesized macrocycles are characterized by a high degree of functionalization, which will be used in the future to apply the principles of dynamic covalent chemistry in the final material synthesis. The internal cavity of these cyclic compounds created by functionalization can be used to bind various molecular guests. The knowledge regarding the synthesis of such macrocycles obtained here will be instrumental in achieving the initially described goal of wet chemical synthesis of 1D organic nanotubes in the future. The methods of macrocyclization were to be used in Chapter 4 to synthesize a chiral aromatic macrocycle based on [5]helicene subunits, but without success. Instead, a byproduct was isolated that proved to be a previously unknown molecular switch. This switch allows reversible generation of a paramagnetic isomer by irradiation at low temperatures. This opens up a completely new class of molecular switches whose potential applications are beyond the scope of this work.
7

Light-controlled energy transfer

Ortego, Javier Moreno 22 July 2015 (has links)
Mit dem Ziel stabile und photomodulierbare Fluorophore für ihre direkte Anwendung in der hochaufgelösten Mikroskopie, wurde die Synthese und Charakterisierung von neuen fern Rot emittierender photoschaltbarer Fluorophore erreicht. Hierbei wurde die elektronische Kopplung zwischen den Komponenten tiefgreifend untersucht, und die Struktur Eigenschafts Beziehung etabliert. Durch die Wechselwirkung der photochromen Einheit mit dem Fluorophor, konnte die Fluoreszenzemission ein- und ausgeschaltet werden. Zusätzlich wurden Einkapselungs Experimente in Micellen durchgeführt, um die Wasserlöslichkeit der synthetisierten Verbindungen zu untersuchen. Letzlich, wurden mögliche Anwendungen mittels Fluoreszenzmikroskopie geprüft. Mit dem Ziel hochaufgelöste Bilder unter biologischen Bedingungen zu erhalten, wurde die Verkapselung der Dyaden in riesige unilamellare Vesikel erprobt. Unter Ausnutzung der Vorteile nichtlinearer Prozesse wurde die Synthese und Charakterisierung von photochromen Verbindungen, die in der Lage indirekt durch einen anfänglichen sensibilisierten Prozess geschaltet werden, untersucht. Zu diesem Zweck wurde ein Triarylamin Chromophor als Zwei-Photonenabsorber kovalent an einen Azobenzol verbunden. Die Charakterisierung der angeregten Zustandsdynamik wurde ausgeführt und die zwei Photonen induzierte Isomerisierung der Dyade bestätigt. Eine detaillierte Untersuchung der elektrochemischen Eigenschaften wurde durchgeführt und Richtlinien zur Verbesserung des Systems wurden kurz genannt. / With the purpose of designing stable and photomodulable fluorophores for their direct application in subdiffraction microscopy techniques, the synthesis and characterization of new far-red emitting photoswitchable fluorophores was accomplished. Fluorescence emission was efficiently modulated or switched On and Off by the interaction of the photochromic unit with the fluorescent-unit. Additionally, encapsulation experiments in micelles were performed to investigate the water solubility of the synthesized compounds. Finally, potential applications were examined with fluorescence microscopy, encapsulating the dyads in giant uni-lamellar vesicles under biological conditions to explore the feasibility to obtain highly resolved subdiffraction images. Exploiting the advantages of nonlinear processes, the synthesis and characterization of photochromes which are able to be switched indirectly through an initial sensitized event were studied. With this determination a two-photon absorbing triarylamine chromophore was covalently linked to an electron poor azobenzene. In-depth characterization of the excited state dynamics was performed and two photon induced isomerization of the dyad was confirmed. A detailed study of the electrochemical properties was set and guidelines towards the improvement of the system were succinctly mentioned.
8

Design and synthesis of photoswitchable polymerization catalysts

Senf, Antti Alexander 04 July 2016 (has links)
Die andauernden Entwicklungen auf dem Gebiet der kontrollierten Polymerisation haben zu zahlreichen neuen Methoden geführt, um klar definierte Polymere zu synthetisieren. Die dabei entstehenden molekularen Strukturen haben einen großen Einfluss auf die makroskopischen Eigenschaften. Hier werden Ansätze beschrieben um Polymerisation in situ zu steuern, was zur besseren Kontrolle von Polymereigenschaften führen soll. Zu diesem Zweck wurden etablierte organometallische Katalysatoren mit Azobenzolen funktionalisiert, um die Geometrie des Katalysators in situ zu ändern. Zuerst wurde ein Salen-Katalysator synthetisiert, der ein Azobenzol in der Nähe des aktiven Zentrums besitzt. Dieser zeigte vielversprechende photochemische Eigenschaften. Es wurde aber festgestellt, dass die Bestrahlung die LMCT Bande des Metalls anregt, was die Bindung des Polymers zum Katalysator beeinträchtigt. Um dieses Problem zu umgehen wurde ein dinuklearer Salen-Katalysator, mit einer besseren Bandentrennung, synthetisiert. Dieser Katalysator zeigte eine trans-cis-Isomerisierung, konnte photochemisch aber nicht zurück geschaltet werden, da die Absorptionsbanden des Azobenzols mit denen des Metalls überlappten. Daher wurde das Absorptionsverhalten des katalytischen Zentrums durch die Einführung eines rigiden durchkonjugierten Salphen Liganden geändert. Drei Systeme wurden synthetisiert, wobei der Katalysator mit einer Ethylenbrücke zwischen dem Azobenzol und dem Metallzentrum die besten Ergebnisse zeigte. Dieser Katalysator konnte reversibel geschaltet werden und zeigte auch einen Aktivitätsunterschied in der Polymerisation von b-Butyrolacton. Es konnte gezeigt werden, dass die Aktivität des Katalysators um einen Faktor von 2,4 zwischen dem trans-Isomer und dem bestrahlten Reaktionsgesmisch erhöht werden konnte. Das gleiche Ergebnis wurde auch bei in situ Experimenten beobachtet. / Rapid developments in the field of controlled polymerization have led to numerous ways to produce well defined polymeric structures. This influence on the polymeric microstructure allowed a more efficient control over the macroscopic properties as well. Here, approaches are described to in situ control the polymerization outcome, which will eventually lead to a more defined manipulation of polymeric properties. For this purpose well established organometallic catalyst were functionalized with azobenzene moieties to alter the catalysts geometry in situ. First a salen catalyst with an azobenzene in close proximity to the active site was synthesized. The catalyst showed promising photochemical behavior, but irradiation of the catalyst would interfere with the binding of the polymeric chain, due to excitation of the metal’s LMCT band. To overcome this challenge a dinuclear salen catalysts with a better separation of the bands was synthesized that would allow control over cooperative effects. This catalysts showed trans-cis-isomerization but no photochemical back-reaction, due to an overlap of the absorption bands of the cis-azobenzene with the metal moiety. Therefore, the absorption of the catalytically active moiety was altered by introducing a rigid fully conjugated salphen system as the ligand. Three systems were synthesized, of which an ethylene bridged ligand showed the best results. It allowed reversible switching between both states and showed an activity change in the polymerization of b-butyrolactone. The catalyst showed an increased activity by a factor of 2.4 in the trans-isomer compared to the photostationary state and it also allowed for an in-situ switching between both states without affecting the efficiency of the system.
9

Light-Controlled Mechanically Interlocked Molecules and Materials

Boelke, Jan 28 March 2024 (has links)
Im Zusammenhang mit auf Reize reagierenden Materialien ist Licht aufgrund seiner hohen räumlichen und zeitlichen Auflösung von besonderer Bedeutung. Hierfür können molekulare Photoschalter, wie z.B. Azobenzole, in das Material eingebaut werden, um eine Reaktion auf Lichteinstrahlung von der molekularen auf die makroskopische Ebene zu übertragen. Fortschrittliche Moleküldesigns, wie z.B. Ortho-Fluorierung, führen dabei zu hervorragenden bistabilen Photoschaltern, die in Kombination mit Cyclodextrinen (CDs) als supramolekulare Bausteine eine Vielfalt an lichtempfindlichen Materialien ermöglichen. Um ein grundlegendes Verständnis der Wechselwirkungen von ortho-Fluorazobenzolen (FAzos) mit CDs zu erlangen, wurde in Kapitel II deren supramolekulare Wirt-Gast-Komplexierung untersucht. Hierbei konnte eine veränderte Barriere des Auffädelns der CDs beobachtet werden. Durch detaillierte Untersuchungen an polymeren Modellverbindungen in Kapitel III konnte gezeigt werden, dass das Auffädeln über die Z- im Vergleich zu den E-Isomeren der FAzos deutlich reduziert ist und dadurch die Bildung von Pseudo-Polyrotaxanen durch Bestrahlung mit Licht kontrolliert werden kann. Durch speziell konzipierte DOSY-Experimente konnte die Abfädelungskinetik aus Polyrotaxanen, bei denen die CDs durch das Z-Azobenzol auf der Achse fixiert wurden, verfolgt werden. Somit konnte gezeigt werden, dass eine Kontrolle der Bewegung von CDs durch Licht möglich ist. Auf Grundlage dieser Ergebnisse wurden in Kapitel IV neuartige lichtempfindliche Slide-Ring Materialien entwickelt, die bei Lichteinstrahlung eine reversible Änderung ihrer Steifigkeit aufweisen. Die Materialien wurden so konzipiert, dass sie ortho-Fluorazobenzole enthalten, die als durch Licht schaltbare Barrieren für das Gleiten von CDs entlang des Polymerrückgrats dienen. Hierdurch konnte eine reversible Änderung des Elastizitätsmoduls durch Bestrahlung mit Licht erzielt werden und somit ein erfolgreicher Konzeptnachweis erbracht werden. / In the context of stimuli-responsive materials, light is of particular importance due to its high spatial and temporal resolution. For this purpose, molecular photoswitches, such as azobenzenes, can be incorporated into the material to transfer a response to light irradiation from the molecular to the macroscopic level. Advanced molecular designs, such as ortho-fluorination, lead to excellent bistable photoswitches which, in combination with cyclodextrins (CDs) as supramolecular building blocks, enable a variety of light-responsive materials. To gain a fundamental understanding of the interactions of ortho-fluoroazobenzenes (FAzos) with CDs, their supramolecular host-guest complexation was investigated in Chapter II. An altered barrier for the threading of CDs was thereby observed. Detailed studies on polymeric model compounds in Chapter III showed that threading over the Z-isomers of the FAzos is significantly reduced compared to the E-isomers and that the formation of pseudo-polyrotaxanes can thus be controlled by irradiation with light. Using specially designed DOSY experiments, the threading kinetics from polyrotaxanes, in which the CDs where fixed on the axis by the Z-azobenzene, could be followed. This showed that it is possible to control the movement of CDs by light. Based on these results, novel photoresponsive slide-ring materials were developed in Chapter IV, which exhibit a reversible change in stiffness when exposed to light. The materials were designed to contain ortho-fluoroazobenzenes, which serve as photoswitchable barriers for the sliding of CDs along the polymer backbone. This enabled a reversible change of the elastic modulus to be accomplished by irradiation with light, thus providing a successful proof of concept.
10

The syntheses, NMR and photochromic properties of modified dimethyldihydropyrenes

Zhang, Rui 06 November 2007 (has links)
The cyclopentadienone-fused dihydropyrenes 46 and 47 were synthesized. The internal methyl resonances, the coupling constants, NICS calculations and X-ray results confirmed that the cyclopentadienone displays antiaromatic character resulting in bond localization in the annulene ring consistent with a 4n-pi fused system. The ring current of the dihydropyrene fragment is reduced by fusion of the antiaromatic system by about 80% of that caused by benzene. The syntheses of the methylfulvene fused dihydropyrene 56 and the phenylfulvene fused dihydropyrene 58 have been accomplished. The calculated and experimental NMR data and NICS calculations all demonstrated that the fulvenes had weak diatropic ring currents and caused bond localizations in the DHP rings, in which phenyl fulvene has a larger effect than that of methyl fulvene. A number of bis-dihydropyrene systems, bis-dihydropyrene ketone 117, bis-benzo[e]dihydropyrene ketone 119, benzo[e]dihydropyrene dihydropyrene ketone 122, bis-benzo[e]dihydropyrene methylene 124 and the benzo[e]dihydropyrene- dihydropyrene acetylene 130, have been synthesized, in which 117, 119 and 124 are homo-systems and 122 and 130 are hetero-systems. The multiple photoswitching properties study found that all of these systems except 130 showed multi-states during the photo opening and photo closing processes, which means that each end of the DHP units photo opens or closes separately rather than synchronously. In the homo switches 117, 119 and 124, the two DHP units act independently, but the relative differentiation is not very significant. On the other hand, the hetero-switch 122 showed fully differentiated photo opening process and almost a pure open-closed intermediate 122’ could be achieved. This is the first example which clearly showed four states in the UV closing process. The relative photo opening and closing rates compared to benzoDHP 36 have also been studied. It was found that while the carbonyl linker largely increased the relative photo opening rate (117, 119 and 122), the methylene linker only increased it slightly (124). The photo closing processes were always fast as usual. The studies of the thermal return reactions of these systems showed that while the carbonyl linker substantially slowed down the thermal return reactions of the DHP units (117, 119 and 122), the methylene linker speeded it up slightly (124). The mono-iron tricarbonyl benzo[e]dihydropyrene complex 152, the bis-iron tricarbonyl benzo[e]dihydropyrene complex 153 and the iron tetracarbonyl dihydropyrene complex 151 were synthesized. The structures of 152 and 153 were determined by X-ray crystallography. The coordinations of iron tricarbonyl moieties to the DHP rings caused a distortion of ca. 30 degree away from the central DHP plane. Coordination also increased bond alternation and reduced ring currents in the DHP rings. 1H-NMR and X-ray studies showed that 152 showed a weak paratropic ring current in the DHP ring. Iron coordination of the DHP completely stopped the photochromic properties of the dihydropyrenes.

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