Two-photon absorption of metal-organic DNA-probes
ABSTRACT We report remarkable multiphoton absorption properties of DNA intercalating ruthenium complexes: (1) [Ru(phen)(2)dppz](2+); (2) [(11,11'-bidppz)(phen)(4)Ru(2)](4+); (3) [11,11'-bipb(phen)(4)Ru(2)](4+). Two-photon spectra in the range from 460 to 1100 nm were measured using the Z-scan technique. In particular, complex 2 was found to exhibit very strong two- and three-photon absorption properties, which could be an effect of symmetric charge transfer from the ends towards the middle of the conjugated dimeric orbital system. We propose that these molecules could provide a new generation of DNA binding nonlinear chromophores for wide applications in biology and material science. The combination of a large two-photon cross section and strong luminescence quantum yields for the molecules when intercalated makes the compounds uniquely bright and photo-stable probes for two-photon luminescence imaging and also promising as enhanced photosensitizers in two-photon sensitizing applications.
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- "Sznitko et al.  successfully demonstrated amplified spontaneous emission and lasing action in deoxyribonucleic acid blended with cetyltrimethyl-ammonium chloride surfactant and doped with 3-(1,1-dicyanoethenyl1)-1phenyl-4,5dihydro-1H-pyrazol e organic dye. Hanczyc et al.  observed remarkable multiphoton absorption properties of DNA intercalating ruthenium complexes: 1) [Ru(phen) "
ABSTRACT: We present our results from the measurements of third-order optical nonlinearity in DNA doped Rhodamine 6G/PVA films achieved through Z-scan measurements using ~2 picosecond (ps) pulses at a wavelength of 800 nm. The films demonstrated negative nonlinear refractive index (n 2) with magnitudes of (0.065 -2.89) × 10 –14 cm 2 /W with varying concentration of DNA. Open aperture data demonstrated strong two-photon absorption with a magnitude of ~1.6 cm/GW for films doped with 2 wt% of DNA. The recovery time of excited state population, retrieved from the degen-erate pump-probe experimental data, was <4 ps. These data suggests that DNA is promising material for applications such as optical switching.Optics and Photonics Journal 01/2012; 2(03):135-139. DOI:10.4236/opj.2012.23019
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ABSTRACT: N-arylpyrrole-based dyes possessing excellent opto-electronic properties are promising candidates for two-photon fluorescence labeling materials. The systematic investigation of novel N-arylpyrrole derivatives is of great importance for both fine-tuning electronic spectra and designing two-photon absorption (2PA) materials. We thoroughly studied influences of the π-conjugated center and N-substituted pyrrole moieties on the linear optical and 2PA properties. Our results show that introducing N-arylpyrrole produces bathochromic-shifts of the absorption and emission bands and an enhancement of the 2PA cross section (δ(max)), demonstrating that the electron-rich pyrrole moieties can efficiently increase intramolecular charge transfer. Substitution of fluorenyl with benzothiadiazole produces the lower energy gap, higher emission lifetime, red-shift of 2PA spectra and larger δ(max). The absorption and emission bands are highly dependent on the nature of the active building blocks. The aromatic rings attached to pyrrole can modulate the absorption peaks in the high energy and thus subtly modify the electronic properties.Organic & Biomolecular Chemistry 08/2012; 10(37):7527-35. DOI:10.1039/c2ob25916h · 3.49 Impact Factor
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ABSTRACT: A stretched poly(vinyl alcohol) (PVA) film provides a unique matrix that enables also short DNA oligonucleotide duplex to be oriented and studied by linear dichroism (LD). This matrix further allows controlling DNA secondary structure by proper hydration (A or B form), and such humid films could potentially also mimic the molecular crowding in cellular contexts. However, early attempts to study intercalators and groove binders for probing DNA in PVA failed due to competitive matrix binding. Here we report the successful orientation in PVA of DNA oligonucleotide duplex hairpins with thread-intercalated binuclear complex [μ-(11,11'-bidppz)(phen)4Ru2]4+, and how LD depends on oligonucleotide sequence and metal center chirality. Opposite enantiomers of the ruthenium complex, ΔΔ and ΛΛ, were investigated with respect to enantioselectivity toward GC stretches as long as 22 bp. LD, supported by emission kinetics, reveals that threading intercalation occurs only with ΔΔ whereas ΛΛ remains externally bound, probably in either or both of the grooves of the GC-DNA. Enantioselective binding properties of sterically rigid DNA probes such as the ruthenium complexes could find applications for targeting nucleic acids, e.g., to inhibit transcription in therapeutic context such as treatment of malaria or cancer.The Journal of Physical Chemistry B 02/2013; 117(10). DOI:10.1021/jp311952x · 3.30 Impact Factor