Photobehaviour and DNA interaction of styrylquinolinium salts bearing thiophene substituents

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spectral properties and photophysics of arylacetylenes in thin films

AbstractWe report the photobehaviour of a series of eight structurally related arylacetylene derivatives, in solution as well as in pristine and PC61BM blended thin-_lms. The formation of both H- and J-aggregates in the solid state have been demonstrated, and, interestingly, an energy transfer from H-aggregates or/and from residual "unstacked" molecules to J-aggregates has been found, the latter being the only emitting species. The fuorescence quenching by PC61BM at di_erent loadings has been studied in blend films, and it has been found particularly effcient in the case of a symmetrical peripheral substitution of the acetylene derivative core. Preliminary time-resolved measurements in emission (ns resolution) and in absorption (fs resolution) con_rmed the H⟶J energy transfer and underlined the presence of delayed fuorescence from Jaggregates, formed by energy transfer from the long-lived first excited singlet state of H-aggregates. In all cases, a homogeneous surface morphology of thin films

Uncovering Structure-Property Relationships in Push-Pull Chromophores: A Promising Route to Large Hyperpolarizability and Two-Photon Absorption

In this investigation, we report the first hyperpolarizabilities and two-photon absorption cross sections of a large series of 12 push–pull cationic chromophores. All of these dyes show a dipolar acceptor+–π–donor structure, where the nature of the donor and acceptor units and π-bridge was synthetically tuned to allow insightful comparisons among the molecules. The hyperpolarizability was obtained through a solvatochromic method, by exploiting the rare negative solvatochromism exhibited by the investigated compounds. The two-photon absorption cross sections were determined through two-photon excited fluorescence measurements by means of a tunable nanosecond laser system for sample excitation. The nonlinear optical properties were discussed relatively to the photoinduced intramolecular charge transfer occurring in these donor–acceptor systems, investigated by femtosecond transient absorption experiments. We found a strong increase in hyperpolarizability upon increasing the molecular conjugation. Unexpectedly, the hyperpolarizability is almost unaffected by an increase in donor/acceptor strength and intramolecular charge transfer degree. Differently, the two-photon absorption cross sections of these dyes are enhanced by an increase in both molecular conjugation and intramolecular charge transfer efficiency. Several recent literature works have reported at the same time scattered information about the hyperpolarizability and two-photon absorption of small organic molecules. Our investigation is, to the best of our knowledge, the first attempt to uncover detailed structure–property relationships for these two nonlinear optical properties. Our results represent a promising route to achieve large hyperpolarizability and two-photon absorption in push–pull dyes and may drive the design of new efficient nonlinear optical materials

Transient absorption spectroscopic studies on 4-nitroquinoline N-oxide: From femtoseconds to microseconds timescale

[EN] The singlet excited state of 4-nitroquinoline N-oxide ((1)NQNO*) has been characterized by different spectroscopic techniques, combining transient absorption with steady state and time-resolved emission spectroscopy. The energy of (1)NQNO* has been established as 255 kJ/mol from the fluorescence spectrum, whereas its lifetime has been found to be 10 ps in the femto-laser flash photolysis (LFP) experiments, where a characteristic S-1-S-n absorption band with maximum centered at 425 nm is observed. In a first stage, the triplet excited state of NQNO ((3)NQNO*) has also been characterized by emission spectroscopy in solid matrix, at low temperature. Thus, from the steady state phosphorescence spectrum the triplet energy has been estimated as 183 kJ/mol, whereas the setup with time resolution has allowed us to determine the phosphorescence lifetime as 3 ms. Formation of (3)NQNO* by intersystem crossing in solution at room temperature, has been monitored by femto-LFP, which shows the appearance of a band with maximum at 560 nm (T-1-T-n). It increases with the decreasing intensity of its precursor 425 nm(S-1-S-n) band, giving rise to an isosbestic point at 500 nm. The characterization of (3)NQNO* has been completed by nano-LFP, using xanthone as photosensitizer and oxygen as well as beta-carotene as quenchers. In addition, quenching of (3)NQNO* by electron donors (DABCO) is also observed in aprotic solvents, leading to the radical anion of NQNO (.(-)NQNO). If there is a proton source in the medium (Et3N as electron donor or MeCN:H2O/4:1 as solvent system) protonation of the radical anion results in formation of the neutral radical of NQNO (.NQNOH). In general, all processes are slower in protic solvents because of the solvation sphere. Overall, this information provides a deeper insight into the formation and behavior of excited states and radical ionic species derived from the title molecule NQNO. (C) 2019 Elsevier B.V. All rights reserved.The work was financially supported by the Regional Government of Generalitat Valenciana (PROMETEO/2017/075) as well as the Spanish Government Science Department with the CTQ-2016-78875-P and CTQ-2009-13699 projects and the N. D.-G. fellowship (BES-2010-035875). BC, CC and FE acknowledge MIUR and the University of Perugia for financial support to the project AMIS, through the program "Dipartimenti di Eccellenza - 2018-2022"Duran-Giner, N.; Carlotti, B.; Clementi, C.; Elisei, F.; Encinas Perea, S.; Miranda Alonso, MÁ. (2019). Transient absorption spectroscopic studies on 4-nitroquinoline N-oxide: From femtoseconds to microseconds timescale. Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy. 216:265-272. https://doi.org/10.1016/j.saa.2019.02.105S265272216Fuchs, T., Gates, K. S., Hwang, J.-T., & Greenberg, M. M. (1999). Photosensitization of Guanine-Specific DNA Damage by a Cyano-Substituted Quinoxaline Di-N-oxide. Chemical Research in Toxicology, 12(12), 1190-1194. doi:10.1021/tx990149sDaniels, J. S., & Gates, K. S. (1996). DNA Cleavage by the Antitumor Agent 3-Amino-1,2,4-benzotriazine 1,4-Dioxide (SR4233):  Evidence for Involvement of Hydroxyl Radical. Journal of the American Chemical Society, 118(14), 3380-3385. doi:10.1021/ja9510774Jerina, D. M., Boyd, D. R., & Daly, J. W. (1970). Photolysis of pyridine-N-oxide: an oxygen atom transfer model for enzymatic oxygenation, arene oxide formation, and the NIH shift. Tetrahedron Letters, 11(6), 457-460. doi:10.1016/0040-4039(70)80074-0Albini, A., & Alpegiani, M. (1984). The photochemistry of the N-oxide function. Chemical Reviews, 84(1), 43-71. doi:10.1021/cr00059a004Winkle, S. A., & Tinoco, I. (1978). Interactions of 4-nitroquinoline 1-oxide with four deoxyribonucleotides. Biochemistry, 17(7), 1352-1356. doi:10.1021/bi00600a033Sheng, Z., Song, Q., Gao, F., Zhou, X., Li, J., Dai, J., … Ma, X. (2000). A laser flash photolysis study of amino acids and dipeptides using 4-nitroquinoline 1-oxide as a photosensitizer: The pH dependence. Research on Chemical Intermediates, 26(7-8), 715-725. doi:10.1163/156856700x00633Yamakawa, M., Kubota, T., Ezumi, K., & Mizuno, Y. (1974). Absorption and phosphorescence spectra of 4-nitropyridine N-oxides and 4- and 3-nitroquinoline N-oxides. Spectrochimica Acta Part A: Molecular Spectroscopy, 30(11), 2103-2119. doi:10.1016/0584-8539(74)80061-9Kubota, T., Yamakawa, M., & Mizuno, Y. (1972). The Singlet-triplet Absorption Spectra of Heterocyclic AmineN-Oxides (I). Bulletin of the Chemical Society of Japan, 45(11), 3282-3286. doi:10.1246/bcsj.45.3282Kasama, K., Takematsu, A., Yamamoto, S., & Arai, S. (1984). Photochemical reactions of 4-nitroquinoline 1-oxide with DNA and related compounds. The Journal of Physical Chemistry, 88(21), 4918-4921. doi:10.1021/j150665a025Dutta Choudhury, S., & Basu, S. (2006). Interaction of 4-Nitroquinoline-1-oxide with Indole Derivatives and Some Related Biomolecules:  A Study with Magnetic Field. The Journal of Physical Chemistry B, 110(17), 8850-8855. doi:10.1021/jp055971lSeki, H., Takematsu, A., & Arai, S. (1987). Photoinduced electron transfer from amino acids and proteins to 4-nitroquinoline 1-oxide in aqueous solutions. The Journal of Physical Chemistry, 91(1), 176-179. doi:10.1021/j100285a038Shi, X., & Platz, M. S. (2004). Time Resolved Spectroscopy of Some Aromatic N-Oxide Triplets, Radical Anions, and Related Radicals. The Journal of Physical Chemistry A, 108(20), 4385-4390. doi:10.1021/jp037708vEzumi, K., Kubota, T., Miyazaki, H., & Yamakawa, M. (1976). Electronic spectra of the anion radicals of heterocyclic amine N-oxides and related substances. The Journal of Physical Chemistry, 80(9), 980-988. doi:10.1021/j100550a012Daniels, J. S., Gates, K. S., Tronche, C., & Greenberg, M. M. (1998). Direct Evidence for Bimodal DNA Damage Induced by Tirapazamine. Chemical Research in Toxicology, 11(11), 1254-1257. doi:10.1021/tx980184jBosca, F., Encinas, S., Heelis, P. F., & Miranda, M. A. (1997). Photophysical and Photochemical Characterization of a Photosensitizing Drug:  A Combined Steady State Photolysis and Laser Flash Photolysis Study on Carprofen. Chemical Research in Toxicology, 10(7), 820-827. doi:10.1021/tx9700376Carlotti, B., Cesaretti, A., Fortuna, C. G., Spalletti, A., & Elisei, F. (2015). Experimental evidence of dual emission in a negatively solvatochromic push–pull pyridinium derivative. Physical Chemistry Chemical Physics, 17(3), 1877-1882. doi:10.1039/c4cp04963bCesaretti, A., Carlotti, B., Gentili, P. L., Clementi, C., Germani, R., & Elisei, F. (2014). Spectroscopic Investigation of the pH Controlled Inclusion of Doxycycline and Oxytetracycline Antibiotics in Cationic Micelles and Their Magnesium Driven Release. The Journal of Physical Chemistry B, 118(29), 8601-8613. doi:10.1021/jp502278zCarlotti, B., Cesaretti, A., & Elisei, F. (2012). Complexes of tetracyclines with divalent metal cations investigated by stationary and femtosecond-pulsed techniques. Phys. Chem. Chem. Phys., 14(2), 823-834. doi:10.1039/c1cp22703

Findings from the Hackathon on Understanding Euroscepticism Through the Lens of Textual Data

We present an overview and the results of a shared-task hackathon that took place as part of a research seminar bringing together a variety of experts and young researchers from the fields of political science, natural language processing and computational social science. The task looked at ways to develop novel methods for political text scaling to better quantify political party positions on European integration and Euroscepticism from the transcript of speeches of three legislations of the European Parliament

Replication Data for: The odd couple: Analysing UKIP and FSM’s EU-opposition in the EP

Since the late 2000s economic and immigration crises are testing the European Union (EU). Such challenges have opened up a period of radical change for the EU, among them, the Brexit referendum that will radically change EU’s geography. This turmoil is mirrored by the last European Parliament (EP) election results; extreme right and left wing parties succeeded in the electoral competition at the expense of their mainstream counterpart. These forces are generally labelled as ‘Eurosceptic’, even though the literature still lacks a clear-cut definition of Euroscepticism. Starting from this observation, this paper reviews the conceptual evolution of Euroscepticism, stressing its pros and cons and proposes a reconceptualisation of it in terms of EU-opposition such that the objects of criticism are clearly identified as the EU-policies, the EU-elite, the EU-regime and the EU-community. The paper applies ‘EU-opposition’ to examine empirically the activity of two ‘Eurosceptic’ parties in the EP: the Italian Five Stars Movement (FSM) and the British United Kingdom Independence Party (UKIP), using the speeches they deliver in the arena of the EP as the main source of data. From the analysis, it can be seen that UKIP and FSM are an odd couple working in the same party-group in the EP, and the concept of EU-opposition is able to better disentangle UKIP and FSM’s criticism of the EU

Replication Data for: The odd couple: analyzing United Kingdom Independence Party (UKIP) and Italian Five Stars Movement’s (FSM’s) European Union (EU)-opposition in the European Parliament

Since the late 2000s economic and immigration crises are testing the European Union (EU). Such challenges have opened up a period of radical change for the EU, among them, the Brexit referendum that will radically change EU’s geography. This turmoil is mirrored by the last European Parliament (EP) election results; extreme right and left wing parties succeeded in the electoral competition at the expense of their mainstream counterpart. These forces are generally labelled as ‘Eurosceptic’, even though the literature still lacks a clear-cut definition of Euroscepticism. Starting from this observation, this paper reviews the conceptual evolution of Euroscepticism, stressing its pros and cons and proposes a reconceptualisation of it in terms of EU-opposition such that the objects of criticism are clearly identified as the EU-policies, the EU-elite, the EU-regime and the EU-community. The paper applies ‘EU-opposition’ to examine empirically the activity of two ‘Eurosceptic’ parties in the EP: the Italian Five Stars Movement (FSM) and the British United Kingdom Independence Party (UKIP), using the speeches they deliver in the arena of the EP as the main source of data. From the analysis, it can be seen that UKIP and FSM are an odd couple working in the same party-group in the EP, and the concept of EU-opposition is able to better disentangle UKIP and FSM’s criticism of the EU

The different twins A multilevel analysis of the positions of the Northern League and the Five Star Movement on the integration-demarcation dimension

According to several scholars, the politicization of issues connected to immigration and the European Union (EU) has generated a new cleavage that now structures political competition in Western Europe. Italy is an interesting case for studying this process, as two ‘different’ populist-Eurosceptic parties, namely the Northern League (LN) and the Five Star Movement (M5S), significantly increased their share of votes in the last round of national elections and eventually managed to form a governmental coalition by politicizing these two issues. This paper proposes a multifaceted conceptualisation of the EU and immigration issues in order to investigate how LN and M5S position themselves across their multiple sub-dimensions. The empirical analysis is based on an original dataset of parliamentary speeches delivered by the two parties’ representatives in two distinct institutional arenas: the Italian one and the European Parliament. The results show that LN’s positions are guided by cultural-identitarian and sovereignist arguments, while M5S mobilizes the two issues to boost its anti-elitist claims. Therefore, the paper claims that the governmental coalition between the two parties is driven by office-seeking motivations, rather than by a policy-seeking strategy

Online Hate Speech and the Radical Right in Times of Pandemic: The Italian and English Cases

Social media is considered a particularly conducive arena for hate speech, a form of communication often linked to the radical right. The goal of this study is to offer an empirical contribution that comparatively explores the presence and features of hate speech in the social media discourse of the radical right (leaders and parties) in Italy and the UK during the first year of the pandemic. This mixed-methods study analyses 21,360 tweets using wordcloud analysis (to conceptually map the social media discourse of the radical right and mainstream parties), topic modelling (to identify the main topics of the radical right\u2019s tweets and how they relate to Covid-19) and formalised content analysis (to better understand how hate speech is related to the virus). We find that radical right leaders have managed to bring exclusion-oriented issues to the agenda at this time of crisis, albeit in different ways, by emphasising different understandings of in-groups and out-groups in relation to Covid-19