Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2+2] cycloaddition and cycloreversion

Koelsch S, Ihmels H, Mattay J, Sewald N, Patrick BO. Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2+2] cycloaddition and cycloreversion. Beilstein Journal of Organic Chemistry. 2020;16:111-124.It was demonstrated that styrylquinolizinium derivatives may be applied as photoswitchable DNA ligands. At lower ligand:DNA ratios (<= 1.5), these compounds bind to duplex DNA by intercalation, with binding constants ranging from K-b = 4.1 x 10(4) M to 2.6 x 10(5) M (four examples), as shown by photometric and fluorimetric titrations as well as by CD and LD spectroscopic analyses. Upon irradiation at 450 nm, the methoxy-substituted styrylquinolizinium derivatives form the corresponding syn head-to-tail cyclobutanes in a selective [2 + 2] photocycloaddition, as revealed by X-ray diffraction analysis of the reaction products. These photodimers bind to DNA only weakly by outside-edge association, but they release the intercalating monomers upon irradiation at 315 nm in the presence of DNA. As a result, it is possible to switch between these two ligands and likewise between two different binding modes by irradiation with different excitation wavelengths

Photocontrolled DNA minor groove interactions of imidazole/pyrrole polyamides

Müller S, Paulus J, Mattay J, Ihmels H, Dodero VI, Sewald N. Photocontrolled DNA minor groove interactions of imidazole/pyrrole polyamides. Beilstein Journal of Organic Chemistry. 2020;16:60-70.Azobenzenes are photoswitchable molecules capable of generating significant structural changes upon E-to-Z photoisomerization in peptides or small molecules, thereby controlling geometry and functionality. E-to-Z photoisomerization usually is achieved upon irradiation at 350 nm (pi-pi* transition), while the Z-to-E isomerization proceeds photochemically upon irradiation at >400 nm (n-pi* transition) or thermally. Photoswitchable compounds have frequently been employed as modules, e.g., to control protein-DNA interactions. However, their use in conjunction with minor groove-binding imidazole/pyrrole (Im/Py) polyamides is yet unprecedented. Dervan-type Im/Py polyamides were equipped with an azobenzene unit, i.e., 3-(3-(aminomethyl)phenyl)azophenylacetic acid, as the linker between two Im/Py polyamide strands. Only the (Z)-azobenzene-containing polyamides bound to the minor groove of double-stranded DNA hairpins. Photoisomerization was exemplarily evaluated by H-1 NMR experiments, while minor groove binding of the (Z)-azobenzene derivatives was proven by CD titration experiments. The resulting induced circular dichroism (ICD) bands of the bound ligands, together with the photometric determination of the dsDNA melting temperature, revealed a significant stabilization of the DNA upon association with the ligand. The (Z)-azobenzene acted as a building block inducing a reverse turn, which favored hydrogen bonds between the pyrrole/imidazole amide and the DNA bases. In contrast, the E-configured polyamides did not induce any ICD characteristic for minor groove binding. The incorporation of the photoswitchable azobenzene unit is a promising strategy to obtain photoswitchable Im/Py hairpin polyamides capable of interacting with the dsDNA minor groove only in the Z-configuration

A study of acridine and acridinium-substituted bis(terpyridine)zinc(II) and ruthenium(II) complexes as photosensitizers for O2 (1Δg) generation

The homoleptic zinc(II) and ruthenium(II) metal complexes of bis(tridentate) 9-acridine and 10-methyl-9-acridinium-substituted terpyridines were tested for their suitability as triplet photosensitizers (PS) using the photooxidation of 1,5-dihydroxynaphthalene (DHN) to Juglone as a model reaction. Singlet oxygen (O21Δg) generation is superior or comparable to Ru(bpy)32+ for the acridine complexes, whereas the acridinium complexes are ineffective. The molecular structure of the bis(9-(5-([2,2′:6′,2′′-terpyridin]-4′-yl)thien-2-yl)-10-methylacridinium)zinc(II) complex ([Zn(MeATT)2][PF6]4) is determined by X-ray structure analysis, whereas for other complexes DFT calculations were performed for structural parameters to obtain insights into their electronic properties

SELECTIVITY AND CHARGE-TRANSFER IN PHOTOREACTIONS OF DONOR-ACCEPTOR SYSTEMS .6. SELECTIVITY AND CHARGE-TRANSFER IN PHOTOREACTIONS OF ARENES WITH OLEFINS .1. SUBSTITUTION VERSUS CYCLO-ADDITION

Mattay J. SELECTIVITY AND CHARGE-TRANSFER IN PHOTOREACTIONS OF DONOR-ACCEPTOR SYSTEMS .6. SELECTIVITY AND CHARGE-TRANSFER IN PHOTOREACTIONS OF ARENES WITH OLEFINS .1. SUBSTITUTION VERSUS CYCLO-ADDITION. Tetrahedron. 1985;41(12):2393-2404

RADICAL IONS AND PHOTOCHEMICAL CHARGE-TRANSFER PHENOMENA .17. CHARGE-TRANSFER AND RADICAL IONS IN PHOTOCHEMISTRY

Mattay J. RADICAL IONS AND PHOTOCHEMICAL CHARGE-TRANSFER PHENOMENA .17. CHARGE-TRANSFER AND RADICAL IONS IN PHOTOCHEMISTRY. Angewandte Chemie International Edition in English. 1987;26(9):825-845

BETA-OXA-GAMMA,DELTA-ENONES, .2. REARRANGEMENT AND INTRAMOLECULAR CYCLOADDITION OF 1-CYCLOPENTENYLOXY-2-PROPANONE

Mattay J. BETA-OXA-GAMMA,DELTA-ENONES, .2. REARRANGEMENT AND INTRAMOLECULAR CYCLOADDITION OF 1-CYCLOPENTENYLOXY-2-PROPANONE. Tetrahedron Letters. 1980;21(24):2309-2312

SELECTIVITIES IN PHOTOCYCLOADDITIONS OF ARENES TO OLEFINS

Mattay J. SELECTIVITIES IN PHOTOCYCLOADDITIONS OF ARENES TO OLEFINS. Journal of Photochemistry. 1987;37(1):167-183

The Many Facets of Photochemistry

Mattay J. The Many Facets of Photochemistry. Angewandte Chemie. International Ed. 2006;45(22):3570-3571

SELECTIVITY AND CHARGE-TRANSFER IN PHOTOREACTIONS OF DONOR-ACCEPTOR SYSTEMS .7. SELECTIVITY AND CHARGE-TRANSFER IN PHOTOREACTIONS OF ARENES WITH OLEFINS .2. MODE OF CYCLO-ADDITION

Mattay J. SELECTIVITY AND CHARGE-TRANSFER IN PHOTOREACTIONS OF DONOR-ACCEPTOR SYSTEMS .7. SELECTIVITY AND CHARGE-TRANSFER IN PHOTOREACTIONS OF ARENES WITH OLEFINS .2. MODE OF CYCLO-ADDITION. Tetrahedron. 1985;41(12):2405-2417