Design and synthesis of a photoswitchable guanidine catalyst

• Philipp Viehmann and
• Stefan Hecht

Beilstein J. Org. Chem. 2012, 8, 1825–1830, doi:10.3762/bjoc.8.209

• rac-lactide in order to explain the findings. Keywords: azobenzenes; guanidines; molecular switches; organocatalysis; photochromism; ring opening polymerization; Introduction The macroscopic properties of a given polymer, e.g., the glass-transition temperature, morphology, density and tensile

Control over molecular motion using the cis–trans photoisomerization of the azo group

• Estíbaliz Merino and
• María Ribagorda

Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119

• .8.119 Abstract Control over molecular motion represents an important objective in modern chemistry. Aromatic azobenzenes are excellent candidates as molecular switches since they can exist in two forms, namely the cis (Z) and trans (E) isomers, which can interconvert both photochemically and thermally

• external stimuli. Keywords: azobenzenes; molecular switches; nanomachines; photoisomerization; Review This review is based on an article published in 2009 in Anales de Química (Real Sociedad Española de Química) [1]. Azobenzene was described for the first time in 1834 [2] and one century later, in 1937

• ]. On the other hand, the isomerization can also occur through a rotation mechanism [11][30], which involves a π→π* transition (S0→S2) (Figure 3). This mechanism is similar to that produced in the isomerization of stilbene [23]. Azobenzenes as molecular switches A molecular switch is a molecular system

The effect of the formyl group position upon asymmetric isomeric diarylethenes bearing a naphthalene moiety

• Renjie Wang,
• Shouzhi Pu,
• Gang Liu and
• Shiqiang Cui

Beilstein J. Org. Chem. 2012, 8, 1018–1026, doi:10.3762/bjoc.8.114

• of biomolecules in organisms, exemplified by its use in fluorescent probes, fluorescence imaging, and molecular switches in logic circuits [15][16][17][18][19][20][21][22]. In general, in order to efficiently realize the artificial induction of photosensitivity in biomolecules, the photoactive

Recent advances towards azobenzene-based light-driven real-time information-transmitting materials

• Jaume García-Amorós and
• Dolores Velasco

Beilstein J. Org. Chem. 2012, 8, 1003–1017, doi:10.3762/bjoc.8.113

• fast relaxation times for azobenzene-based photochromic molecular switches is still a challenge. This review focuses on the most recent achievements on azobenzene-based light-driven real-time information-transmitting systems. Besides, the main relationships between the structural features of the azo

• -chromophore and the thermal cis-to-trans isomerisation, the kinetics and mechanism are also discussed as a key point for reaching azoderivatives endowed with fast thermal back-isomerisation kinetics. Keywords: kinetics; light-controlled materials; molecular switches; photochromic switches; push–pull

• elements in many devices, such as optical systems for opto-electronics, holographic materials and multicolour displays. Hence, there is a high motivation for the molecular design and study of innovative materials for this purpose. “Molecular switches” denote molecular systems, either small molecules or

Toward unidirectional switches: 2-(2-Hydroxyphenyl)pyridine and 2-(2-methoxyphenyl)pyridine derivatives as pH-triggered pivots

• Christina Tepper and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2012, 8, 977–985, doi:10.3762/bjoc.8.110

• unidirectionally at the molecular level. If a 2-(2-methoxyphenyl)pyridine derivative is fixed to a chiral cyclopeptidic scaffold, a unidirectional progress of the rotation is achieved macroscopically. Keywords: CD spectroscopy; chirality; molecular modeling; molecular switches; unidirectional movements

• complexes the metal ions better than the 2,2′-biypridine unit does. 2-(2-Hydroxyphenyl)pyridine and 2-(2-methoxyphenyl)pyridine should show a similar behavior (see Scheme 1) and therefore should also be applicable as pivots in molecular switches. While 2,2′-biypridine derivatives have been intensively used

• for molecular devices [49][50][51][52][53][54][55][56], 2-(2-hydroxyphenyl)pyridine and 2-(2-methoxyphenyl)pyridine derivatives, to our best knowledge, have only been used as ligands for metal complexes, but not for the construction of molecular switches [57][58][59][60][61][62][63]. Similar compounds

Synthesis and anion recognition properties of shape-persistent binaphthyl-containing chiral macrocyclic amides

• Marco Caricato,
• Nerea Jordana Leza,
• Claudia Gargiulli,
• Giuseppe Gattuso,
• Daniele Dondi and
• Dario Pasini

Beilstein J. Org. Chem. 2012, 8, 967–976, doi:10.3762/bjoc.8.109

• electronic features of the functional groups in the 2,2' positions. Keywords: amides; anion recognition; chirality; macrocycles; molecular switches; supramolecular chemistry; Introduction Macrocyclic molecules possessing a high degree of shape persistency act as molecular cages, and the scientific interest

On the bromination of the dihydroazulene/vinylheptafulvene photo-/thermoswitch

• Virginia Mazzanti,
• Martina Cacciarini,
• Søren L. Broman,
• Christian R. Parker,
• Magnus Schau-Magnussen,
• Andrew D. Bond and
• Mogens B. Nielsen

Beilstein J. Org. Chem. 2012, 8, 958–966, doi:10.3762/bjoc.8.108

• a bromo substituent in the seven-membered ring. Conclusion: Two general procedures for functionalizing the DHA core with a bromo substituent (at positions 3 and 7, respectively) are now available with the DHA as starting material. Keywords: azulene; bromination; dihydroazulene; molecular switches

Diarylethene-modified nucleotides for switching optical properties in DNA

• Sebastian Barrois and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2012, 8, 905–914, doi:10.3762/bjoc.8.103

• results open the way for the use of diarylethenes as photochromic compounds in DNA-based architectures. Keywords: absorption; cross coupling; molecular switches; oligonucleotide; palladium; photochromism; Introduction The well-defined photoinduced switching of the optical and electronic properties of

Multistep organic synthesis of modular photosystems

• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2012, 8, 897–904, doi:10.3762/bjoc.8.102

• fill them with functional π-stacks of free choice. Keywords: asparagusic acid; charge-transfer cascades; chromophores; disulfide exchange; hydrazone exchange; molecular switches; naphthalenediimides; π-stacks; surface-initiated polymerization; Introduction The architecture of photosystem 1 is rather

Building photoswitchable 3,4'-AMPB peptides: Probing chemical ligation methods with reducible azobenzene thioesters

• Gehad Zeyat and
• Karola Rück-Braun

Beilstein J. Org. Chem. 2012, 8, 890–896, doi:10.3762/bjoc.8.101

• ; molecular switches; peptides; redox chemistry; Introduction Optical switches not only offer the advantage to elucidate, but also to control biological processes with high spatial and temporal resolution by using light, either in vitro or in vivo [1]. In this context, azobenzenes remain a privileged class

Intramolecular bridges formed by photoswitchable click amino acids

• Christian Hoppmann,
• Ronald Kühne and
• Michael Beyermann

Beilstein J. Org. Chem. 2012, 8, 884–889, doi:10.3762/bjoc.8.100

• ; isomerization; molecular switches; photoswitchable click amino acid; thiol–ene click; Introduction Photoswitchable bridges that are site-specifically incorporated into proteins allow the conformation and activity of proteins to be modulated by light. In contrast to common bivalent thiol reactive azobenzene

meta-Oligoazobiphenyls – synthesis via site-selective Mills reaction and photochemical properties

• Raphael Reuter and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2012, 8, 877–883, doi:10.3762/bjoc.8.99

• revealed that the overall degree of switching was independent of the connected azo-units. However, one of the azobonds in the bis-azobiphenyl is isomerized preferentially despite the high structural similarity. Keywords: azobenzene; cross-coupling reaction; foldamer; molecular switches; photochromism

The importance of the rotor in hydrazone-based molecular switches

• Xin Su,
• Timo Lessing and
• Ivan Aprahamian

Beilstein J. Org. Chem. 2012, 8, 872–876, doi:10.3762/bjoc.8.98

• isomerization; hydrazone; molecular switches; pH activation; structure–property analysis; Findings Nature is full of elegant examples of perfectly designed biological motors and machines [1] that perform delicate and precise tasks. Primitive as they may be, numerous artificial molecular machines [2][3][4][5][6

• ], electrochemical [10][11][12][13], and photochemical stimuli [14][15][16][17][18]. One of the benefits of artificial molecular switches and machines is that their output can be controlled or fine-tuned by altering their components [19][20][21]. A relevant example in this context is Feringa’s overcrowded alkene

Molecular switches and cages

• Dirk Trauner

Beilstein J. Org. Chem. 2012, 8, 870–871, doi:10.3762/bjoc.8.97

• Dirk Trauner Department Chemie und Biochemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5–13, 81377 München, Germany 10.3762/bjoc.8.97 Keywords: molecular switches; Molecular switches can toggle between two (or more) stable states encoding different physical features. They allow

• complex systems to respond to changes in their environment defined by light intensity, pH, temperature or voltage. As such, molecular switches play a key role in biology and information technology and have become important components of advanced materials. Chemists have developed a large number of

• photoswitches continue to emerge and “old friends”, such as azobenzenes are constantly improved and optimized. This is not only true with respect to their photophysical properties but also with regard to their synthetic accessibility. Indeed, as molecular switches are applied in ever-increasing quantities, the

Synthesis, electronic properties and self-assembly on Au{111} of thiolated (oligo)phenothiazines

• Adam W. Franz,
• Svetlana Stoycheva,
• Michael Himmelhaus and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2010, 6, No. 72, doi:10.3762/bjoc.6.72

• relevance in the miniaturization of electronic devices particularly since they could serve as molecular switches, wires, and transistors [2][3][4][5]. As a consequence, the molecule-based bottom-up approach to nanodimensional structured self-assembled monolayers (SAMs) on well-defined metal surfaces has

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

Thematic series on supramolecular chemistry

• Christoph A. Schalley

Beilstein J. Org. Chem. 2009, 5, No. 76, doi:10.3762/bjoc.5.76

• made supramolecular synthesis a powerful tool to construct large and complex chemical architecture from simple building blocks with an inherent program of well-designed binding sites. Based on these concepts, functional supramolecules were developed, among them molecular switches, logic gates