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

• representative oligonucleotides by using automated phosphoramidite chemistry, and characterized with respect to its photochromism in DNA. Results and Discussion Design and synthesis of diarylethene-modified 2’-deoxyuridines 4–6 The typical way to tether fluorophores to oligonucleotides is to use an alkyl chain

• affects its photochromism significantly and reduces its photoswitching abilities. Synthesis and photochromic properties of DNA modified with diarylethene 4 As mentioned in the introduction, in a bottom-up approach nucleic acids can be modified with artificial functionalities by providing the corresponding

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

• by Hartley in 1937 [1] many more compounds showing such a photochromism have been reported [2]. However, the azobenzene moiety still remains one of the most popular “work horses” in this respect [3][4][5][6]. The reason can probably be found in its relatively easy synthetic accessibility combined

Photocycloaddition of aromatic and aliphatic aldehydes to isoxazoles: Cycloaddition reactivity and stability studies

• Axel G. Griesbeck,
• Marco Franke,
• Jörg Neudörfl and
• Hidehiro Kotaka

Beilstein J. Org. Chem. 2011, 7, 127–134, doi:10.3762/bjoc.7.18

• showed the highest thermal stabilities. All oxetanes formed from isoxazoles were highly acid-sensitive and also thermally unstable. Cleavage to the original substrates is dominant and the isoxazole derived oxetanes show type T photochromism. Keywords: isoxazoles; oxetanes; Paternò–Büchi reaction

• . Photochemical ring contraction of isoxazoles 7f–7h. Photocycloaddition of aromatic aldehydes to di- and trimethyl isoxazoles 7d and 7e. Preparative photocycloadditions of 7e with aromatic aldehydes. T-type photochromism of isoxazole–aldehyde pairs. Reductive cleavage of the trimethylisoxazole adduct 9a

A perfluorocyclopentene based diarylethene bearing two terpyridine moieties – synthesis, photochemical properties and influence of transition metal ions

• Falk Wehmeier and
• Jochen Mattay

Beilstein J. Org. Chem. 2010, 6, No. 53, doi:10.3762/bjoc.6.53

• perfluorocyclopentene based diarylethene bearing two terpyridine units is reported. Furthermore studies of the free ligand’s photochromism and investigations regarding the influence of various transition metal ions on the photochromic reaction are presented. The photochromism of the central diarylethene unit is

• strongly dependent on the transition metal present, vice versa the photochromic reaction seems to influence the MLCT transition of a binuclear Ru(II) complex. Keywords: coordination chemistry; diarylethene; photochromism; terpyridine; Introduction 2,2′:6′,2″-Terpyridines have been of great interest over

• expected signals (see Experimental Section and Supporting Information File 1). Photochromism of the free ligand The obtained terpyridine substituted diarylethene 10a shows the anticipated photochromic behavior, undergoing photocyclization under irradiation with UV-light (Scheme 4). Figure 1 shows the

Synthesis of novel photochromic pyrans via palladium- mediated reactions

• Christoph Böttcher,
• Gehad Zeyat,
• Saleh A. Ahmed,
• Elisabeth Irran,
• Thorben Cordes,
• Cord Elsner,
• Wolfgang Zinth and
• Karola Rueck-Braun

Beilstein J. Org. Chem. 2009, 5, No. 25, doi:10.3762/bjoc.5.25

• was investigated by time-resolved absorption spectroscopy in the picosecond time domain. Keywords: benzopyrans; chromenes; naphthopyrans; palladium-mediated coupling reactions; photochromism; Introduction Interest in photoswitchable chromophores for the material and life sciences has increased

• , these allene intermediates can be avoided by the replacement of hydrogen in the immediate vicinity of the two aryl residues (3-position of 2H-1-benzopyrans and 2-position of 3H-naphtho[2,1-b]pyrans). Thereby, the photochromism of benzo- and naphthopyrans is expected to be simplified for biological

• substitution pattern permits detailed nitrile and fluorine spectroscopic probing of the photochromism in solution and on surfaces over a broad temperature range. Furthermore, the closed form of the benzopyran-based ω-amino acid 6 (Scheme 2) might be an ideal photoswitchable β-turn mimetic. Optical stimulation

Reversible intramolecular photocycloaddition of a bis(9-anthrylbutadienyl)paracyclophane – an inverse photochromic system. (Photoactive cyclophanes 5)

• Henning Hopf,
• Christian Beck,
• Jean-Pierre Desvergne,
• Henri Bouas-Laurent,
• Peter G. Jones and
• Ludger Ernst

Beilstein J. Org. Chem. 2009, 5, No. 20, doi:10.3762/bjoc.5.20

• recovered by irradiation at 306 nm or by heating. This ‘inverse’ photochromic system has a potential for optical information storage, compound 4 being stable in visible light, at ambient temperature. Keywords: anthracenes; cyclophanes; inverse photochromism; photocycloaddition; Introduction Photochromism

• established systems show a ‘positive’ photochromism in which the electronic absorption spectrum of the product P is red-shifted [1]. When the electronic absorption spectrum of P is blue-shifted, the photochromism is said to be ‘negative’ or ‘inverse’ [1]. Inverse photochromism is encountered in photoaddition

• of conjugated systems [10][11][12][13][14][15][16][17] and may be interesting for information storage materials because the photoproducts can be operated in visible light. Inverse photochromism was recently observed for some vinylogs of cinnamophanes [18][19], such as compound 1 (Figure 2). Several

Synthesis of spiropyrans: H-abstractions in 3-cycloalkenyloxybenzopyrans

• Satish C. Gupta,
• Mandeep Thakur,
• Somesh Sharma,
• Urmila Berar,
• Surinder Berar and
• Ramesh C. Kamboj

Beilstein J. Org. Chem. 2007, 3, No. 14, doi:10.1186/1860-5397-3-14

• -cycloalkenyloxybenzopyrones involving H-abstraction is reported. How a methyl group on the furyl ring affects the product formation is also investigated. 1. Background Spiropyrans exhibit photochromism due to the photoequilibrium with their open chain analogues merocyanins – a property that makes them a material of choice