Methyl Viologens of Bis‐(4’‐Pyridylethynyl)Arenes – Structures, Photophysical and Electrochemical Studies, and their Potential Application in Biology

Abstract

A series of bis-(4'-pyridylethynyl)arenes (arene= benzene, tetrafluorobenzene, and anthracene) were synthesized and their bis-N-methylpyridinium compounds were investigated as a class of π-extended methyl viologens. Their structures were determined by single crystal X-ray diffraction, and their photophysical and electrochemical properties (cyclic voltammetry), as well as their interactions with DNA/RNA were investigated. The dications showed bathochromic shifts in emission compared to the neutral compounds. The neutral compounds showed very small Stokes shifts, which are a little larger for the dications. All of the compounds showed very short fluorescence lifetimes (< 4 ns). The neutral compound with an anthracene core has a quantum yield of almost unity. With stronger acceptors, the analogous bis-N-methylpyridinium compound showed a larger two-photon absorption cross-section than its neutral precursor. All of the dicationic compounds interact with DNA/RNA; while the com-pounds with benzene and tetrafluorobenzene cores bind in the grooves, the one with an anthracene core intercalates as a consequence of its large, condensed aromatic linker moiety, and it aggregates within the polynucleotide when in excess over DNA/RNA. Moreover, all cationic compounds showed highly specific CD spectra upon binding to ds-DNA/RNA, attributed to the rare case of forcing the planar, achiral molecule into a chiral rotamer, and negligible toxicity toward human cell lines at �10 μM concentrations. The anthracene-analogue exhibited intracellular accumulation within lysosomes, preventing its interaction with cellular DNA/RNA. However, cytotoxicity was evident at 1 μM concentration upon exposure to light, due to singlet oxygen generation within cells. These multi-faceted features, in combination with its two-photon absorption properties, suggest it to be a promising lead compound for development of novel Supporting information for this article is available on the WWW under

Synthesis and Properties of Thieno[2′,3′,4′:4,5]naphtho[1,8-cd]pyridines

“…7.92 (dd, J = 3.0 Hz, J = 1.3 Hz, 1H), 7.65 (dd, J = 4.9 Hz, J = 1.3 Hz, 1H), 7.29−7.48 (m, 11H). 13 (51), 207 (15), 163 (22), 150 (15), 135 (15), 126 (29), 77 (77), 76 (14), 74 (16), 73 (74), 63 (20), 51 (27), 45 (36), 39 (23) (46), 387 (11), 375 (15), 374 (50), 373 (42), 372 (12), 359 (13), 187 (10), 186 (9), 179 (8), 170 (8) (53), 375 (18), 374 (57), 373 (61), 372 (19), 359 (18), 207 (17), 139 (33), 91 (48), 89 (20), 77 (28), 75 (18), 73 (76), 65 (42), 63 (19), 51 (20), 39 (35) (73), 371 (47), 340 (13), 339 (19), 328 (32), 169…”

“…Among polycyclic aromatic hydrocarbons (PAHs), pyrene is one of the most intensively investigated peri-fused PAH motifs in interdisciplinary fields of science owing to its unique characteristics, like unusual long excited state lifetime, excimer/exciplex formation, high charge-carrier mobility, chemical stability, and sensing features . Inspired by these properties and the flexible peripheral modification potential, chemists are continuously engaged in the development of simple and efficient synthetic strategies to prepare diverse libraries of pyrene derivatives with custom-made properties for applications in analytics, biomedicine, and materials science. − Along with direct and indirect methods for the selective peripheral (un)­symmetric functionalization of the K and non-K regions of pyrene, − which exhibit strong position and functional group-dependent photophysical properties, − the doping of heteroatoms into the π-conjugated framework is one of the most fundamental strategies to effectively tailor key electronic structural features and enhance desirable properties, including energy levels, band-gaps, and n- or p-type semiconductor characteristics. − …”

“…IR (ATR, cm −1 ): ṽ= 754 (s), 789 (s), 800 (m), 816 (m), 835 (vs), 1094 (m), 1154 (m), 1222 (s), 1502 (s), 1599 (m), 2213 (w), 2924 (w), 3041 (w), 3114 (w). MS (EI, 70 eV) m/z (%)= 397 (M + , 98), 396(100), 395(46), 368(12), 363(9), 350(9), 198(8). HRMS (EI) m/z: [M + ] calcd for C 25 H 13 NF 2 S, 397.0731; found, 397.0720.…”

Phenylethynylanthracene based push–pull molecular systems: tuning the photophysics through para-substituents on the phenyl ring

“…1 These properties have led these dyes to be functionally employed in OLED materials, [2][3][4] fluorescent sensors, [5][6][7][8][9] solar cells, [10][11][12] optical waveguides 13 as well as in bio-applications. 14,15 The optical properties of anthracene can be enhanced by adding substituents to the core ring and by extending p-conjugations. Acetylene bridged systems can be considered as extended single bonded systems and lack the complicacies that arise for double bonded systems concerning cis-trans isomerization.…”

Alkoxy-Substituted Quadrupolar Fluorescent Dyes

“…These electron densities can be modulated by the introduction of a variety of substituents, that is, electron-donating groups (EDGs) and/or electron-withdrawing groups (EWGs). In addition, heterocyclic units have been introduced ,,− into π-conjugated systems to modulate their photophysical and electrochemical properties. Extended bipyridinium-based cyclophanes − (Ex n Box 4+ ) and their π-conjugated analogues − have been investigated extensively by us in the past.…”