Senyushkina, Tamara

[["dc.bibliographiccitation.firstpage","11820"],["dc.bibliographiccitation.issue","49"],["dc.bibliographiccitation.journal","The Journal of Physical Chemistry A"],["dc.bibliographiccitation.lastpage","11836"],["dc.bibliographiccitation.volume","119"],["dc.contributor.author","Druzhinin, Sergey I."],["dc.contributor.author","Galievsky, Victor A."],["dc.contributor.author","Demeter, Attila"],["dc.contributor.author","Kovalenko, Sergey A."],["dc.contributor.author","Senyushkina, Tamara A."],["dc.contributor.author","Dubbaka, Srinivas R."],["dc.contributor.author","Knoche, Paul"],["dc.contributor.author","Mayer, Peter"],["dc.contributor.author","Grosse, Christian"],["dc.contributor.author","Stalke, Dietmar"],["dc.contributor.author","Zachariasse, Klaas A."],["dc.date.accessioned","2018-11-07T09:47:35Z"],["dc.date.available","2018-11-07T09:47:35Z"],["dc.date.issued","2015"],["dc.description.abstract","From X-ray structure analysis, amino twist angles of 90.0 degrees for 2,4-dimethyl-3-(dimethylamino)benzonitrile (mMMD), 82.7 degrees for 4-(di-tert-butylamino)benzonitrile (DTABN), and 88.7 degrees for 6-cyanobenzoquinuclidine (CBQ) are determined, all considerably larger than the 57.4 degrees of 3,5-dimethyl-4-(dimethylamino)benzonitrile (MMD). This large twist leads to lengthening of the amino-phenyl bond, 143.5 pm (mMMD), 144.1 pm (DTABN), 144.6 pm (CBQ), and 141.4 pm (MMD), as compared with 136.5 pm for the planar 4-(dimethylamino)benzonitrile (DMABN). As a consequence, the electronic coupling between the amino and phenyl subgroups in mMMD, DTABN, CBQ, and MMD is much weaker than in DMABN, as seen from the strongly reduced molar absorption coefficients. The fluorescence spectrum of MMD in n-hexane at 25 degrees C consists of two emissions, from a locally excited (LE) and an intramolecular charge transfer (ICT) state, with a fluorescence quantum yield ratio Phi'(ICT)/Phi(LE) of 12.8. In MeCN, a single ICT emission is found. With mMMD in n-hexane, in contrast, only LE fluorescence is observed, whereas the spectrum in MeCN originates from the ICT state. These differences are also seen from the half-widths of the overall fluorescence bands, which in n-hexane are larger for MMD than for mMMD, decreasing with solvent polarity for MMD and increasing for mMMD, reflecting the disappearance of LE and the onset of ICT in the overall spectra, respectively. From solvatochromic measurements the dipole moments mu(e)(ICT) of MMD (16 D) and mMMD (15 D) are obtained. Femtosecond excited state absorption (ESA) spectra at 22 degrees C, together with the dual (LE + ICT) fluorescence, reveal that MMD in n-hexane undergoes a reversible LE reversible arrow ICT reaction, with LE as the precursor, with a forward rate constant k(a) = 5.6 x 10(12) s(-1) and a back-reaction kd similar to 0.05 x 10(12) s(-1). With MMD in the strongly polar solvent MeCN, ICT is faster: k(a) = 10 x 10(12) s(-1). In the case of mMMD in n-hexane, the ESA spectra show that ICT does not take place, contrary to MeCN, in which ka = 2.5 x 10(12) s(-1). The ICT reactions with MMD and mMMD are much faster than that of the parent compound DMABN in MeCN, with k(a) = 0.24 x 10(12) s(-1). Because of the very short ICT reaction times of 180 fs (MMD, n-hexane), 100 fs (MMD, MeCN), and 400 fs (mMMD, MeCN), it is clear that the picosecond fluorescence decays of these systems appear to be single exponential, due to the insufficient time resolution of 3 ps. It is concluded that the faster LE -> ICT reaction of MMD as compared with DMABN (k(a) = 0.24 x 10(12) s(-1) in MeCN) is caused by a smaller energy gap Delta E(S1,S2) between the lowest singlet excited states and not by the large amino twist angle. Similarly, the larger Delta E(S1,S2) of mMMD as compared with MMD is held responsible for its smaller ICT efficiency (no reaction in n-hexane)."],["dc.description.sponsorship","Alexander von Humboldt Foundation"],["dc.identifier.doi","10.1021/acs.jpca.5b09368"],["dc.identifier.isi","000366339400008"],["dc.identifier.pmid","26559045"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/35143"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","1089-5639"],["dc.title","Two-State Intramolecular Charge Transfer (ICT) with 3,5-Dimethyl-4(dimethylamino)benzonitrile (MMD) and Its Meta-Isomer mMMD. Ground State Amino Twist Not Essential for ICT"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","9304"],["dc.bibliographiccitation.issue","33"],["dc.bibliographiccitation.journal","The Journal of Physical Chemistry A"],["dc.bibliographiccitation.lastpage","9320"],["dc.bibliographiccitation.volume","113"],["dc.contributor.author","Druzhinin, Sergey I."],["dc.contributor.author","Kovalenko, Sergey A."],["dc.contributor.author","Senyushkina, Tamara A."],["dc.contributor.author","Demeter, Attila"],["dc.contributor.author","Januskevicius, Regis"],["dc.contributor.author","Mayer, Peter"],["dc.contributor.author","Stalke, Dietmar"],["dc.contributor.author","Machinek, Reinhard"],["dc.contributor.author","Zachariasse, Klaas A."],["dc.date.accessioned","2018-11-07T11:25:39Z"],["dc.date.available","2018-11-07T11:25:39Z"],["dc.date.issued","2009"],["dc.description.abstract","With 4-fluorofluorazene (FPP4F) and its flexible counterpart 4-fluoro-N-phenylpyrrole (PP4F) an intramolecular charge transfer (ICT) reaction occurs in the singlet excited state in sufficiently polar solvents. The ICT reaction begins to appear in tetrahydrofuran (E = 7.4) for FPP4F and in the more polar 1,2-dichloroethane (epsilon = 10.4) with PP4F, showing its presence by dual fluorescence from a locally excited (LE) and an ICT state. Only LE fluorescence is observed in less polar solvents such as n-hexane. The ICT reaction is more pronounced with FPP4F than for PP4F, due to the smaller energy gal) Delta E(S(1),S(2)) of the former molecule, in accordance with the PICT model. The occurrence of an ICT reaction is confirmed by the ICT dipole moments mu(e)(ICT) of 12 D (FPP4F) and 10 D (PP4F), clearly larger than mu(e)(LE) of similar to 4 D for FPP4F and PP4F. Isoemissive points are found in the fluorescence spectra of FPP4F and PP4F in acetonitrile (MeCN), ethyl cyanide (EtCN), and n-propyl cyanide (PrCN) as a function of temperature, confirming the two-state (LE and ICT) reaction mechanism. From plots of the logarithm of the ICT/LE fluorescence quantum yield ratio versus the reciprocal absolute temperature in these solvents, the ICT reaction enthalpies Delta H are determined, with larger -Delta H values for FPP4F than for PP4F: 19.2 as compared with 14.9 kJ/mol in MeCN, as an example. The picosecond fluorescence decay of PP4F at -45 degrees C becomes slower with decreasing solvent polarity, 5.1 ps (MeCN), 14 ps (EtCN), and 35 ps (PrCN), from which the LE -> ICT reaction rate constant is calculated, decreasing from 19 x 10(10) to 2.1 x 10(10) s(-1) between MeCN and PrCN. The femtosecond LE excited-state absorption spectra of FPP4F and PP4F do not undergo any time development in n-hexane (no ICT reaction), but show a fast ICT reaction in MeCN at 22 degrees C, with decay times of 1.1 ps (FPP4F) and 3.3 ps (PP4F). It is concluded that FPP4F and PP4F have a planar ICT state (PICT model), indicating that a perpendicular twist of the donor and acceptor subgroups in a donor/acceptor molecule is not a requirement for fast and efficient ICT. The molecular structures of FPP4F and PP4F obtained from X-ray crystal analysis reveal that the pyrrole group of PP4F is twisted over an angle theta = 25 degrees relative to the fluorophenyl moiety in the ground state, whereas as expected r-PP4F is practically planar (theta = 2 degrees). The pyrrole-phenyl bond length of FPP4F (140.7 pm) is shorter than that for PP4F (141.8 pm)."],["dc.description.sponsorship","Hungarian Science Foundation [76278]"],["dc.identifier.doi","10.1021/jp903613c"],["dc.identifier.isi","000268796800007"],["dc.identifier.pmid","19719292"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/56672"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","1089-5639"],["dc.title","Intramolecular Charge Transfer with 4-Fluorofluorazene and the Flexible 4-Fluoro-N-phenylpyrrole"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","2693"],["dc.bibliographiccitation.issue","12"],["dc.bibliographiccitation.journal","The Journal of Physical Chemistry A"],["dc.bibliographiccitation.lastpage","2710"],["dc.bibliographiccitation.volume","113"],["dc.contributor.author","Zachariasse, Klaas A."],["dc.contributor.author","Druzhinin, Sergey I."],["dc.contributor.author","Galievsky, Victor A."],["dc.contributor.author","Kovalenko, Sergey A."],["dc.contributor.author","Senyushkina, Tamara A."],["dc.contributor.author","Mayer, Peter"],["dc.contributor.author","Noltemeyer, Mathias"],["dc.contributor.author","Boggio-Pasqua, Martial"],["dc.contributor.author","Robb, Michael A."],["dc.date.accessioned","2018-11-07T08:31:35Z"],["dc.date.available","2018-11-07T08:31:35Z"],["dc.date.issued","2009"],["dc.description.abstract","The fluorescence spectra of 2,4,6-tricyano-NN-dimethylaniline (TCDMA), 2,4,6-tricyano-N-methylaniline (TCMA), and 2,4,6-tricyanoaniline (TCA) consist of a single emission band, even in the polar solvent acetonitrile (MeCN). This indicates that an intramolecular charge transfer (ICT) reaction from the initially prepared locally excited (LE) state does not take place with these molecules, in contrast to 4-(dimethylamino)benzonitrile (DMABN), although the electron accepting capability of the tricyanobenzene moiety in TCDMA, TCMA, and TCA is substantially larger than that of the benzonitrile group in DMABN. In support of this conclusion, the picosecond fluorescence decays of the tricyanoanilines are single-exponential. Only with TCDMA in MeCN at the highest time resolution, double-exponential decays are observed. On the basis of a similar temporal evolution of around 2 ps in the femtosecond excited-state absorption (ESA) spectra of TCDMA in this solvent, the time development is attributed to the presence of two rapidly interconverting S(1) conformers. The same conclusion is reached from CASPT2/CASSCF computations on TCDMA, in which two S(1) minima are identified. The ESA spectra of TCDMA, TCMA, and TCA resemble that of the LE state of DMABN, but are different from its ICT ESA spectrum, likewise showing that an ICT reaction does not occur with the tricyanoanilines. From the luminescence spectrum of TCDMA in n-propyl cyanide at - 160 degrees C, it follows that intersystem crossing and not internal conversion is the main S, deactivation channel. The radiative rate constant of TCDMA in MeCN is smaller than that of TCMA and TCA, which indicates that the S, state of TCDMA has a larger ICT contribution than in the case of TCMA and TCA, in accordance with the results of the calculations, which show that the S(1) state displays ICT valence bond character. Extrapolated gas-phase data for TCDMA and TCA are compared with the results of the computations, revealing a good agreement. The calculations on TCDMA and TCA also lead to the conclusion that the lowest excited singlet state S(1) determines its photophysical behavior, without the occurrence of an LE -> ICT reaction, in the sense that the initially excited LE state has already a strong ICT character and there is no equilibrium between two electronic states with strongly different electronic structures (i.e., LE and ICT with very different dipole moments) leading to dual (LE + ICT) fluorescence."],["dc.identifier.doi","10.1021/jp8078925"],["dc.identifier.isi","000264348800006"],["dc.identifier.pmid","19256484"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/17154"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","1089-5639"],["dc.title","Counterintuitive Absence of an Excited-State Intramolecular Charge Transfer Reaction with 2,4,6-Tricyanoanilines. Experimental and Computational Results"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","8238"],["dc.bibliographiccitation.issue","36"],["dc.bibliographiccitation.journal","The Journal of Physical Chemistry A"],["dc.bibliographiccitation.lastpage","8253"],["dc.bibliographiccitation.volume","112"],["dc.contributor.author","Druzhinin, Sergey I."],["dc.contributor.author","Kovalenko, Sergey A."],["dc.contributor.author","Senyushkina, Tamara A."],["dc.contributor.author","Demeter, Attila"],["dc.contributor.author","Machinek, Reinhard"],["dc.contributor.author","Noltemeyer, Mathias"],["dc.contributor.author","Zachariasse, Klaas A."],["dc.date.accessioned","2018-11-07T11:10:57Z"],["dc.date.available","2018-11-07T11:10:57Z"],["dc.date.issued","2008"],["dc.description.abstract","The fluorescence spectrum of the rigidified 4-cyanofluorazene (FPP4C) in n-hexane consists of a dual emission from a locally excited (LE) and an intramolecular charge-transfer (ICT) state, with an ICT/LE fluorescence quantum yield ratio of Phi'(ICT)/Phi(LE) = 3.3 at 25 degrees C. With the flexible 4-cyano-N-phenylpyrrole (PP4C) in n-hexane, such an ICT reaction also takes place, with Phi'(ICT)/Phi(LE) = 1.5, indicating that for this reaction, a perpendicular twist of the pyrrole and benzonitrile moieties is not required. The ICT emission band of FPP4C and PP4C in n-hexane has vibrational structure, but a structureless band is observed in all other solvents more polar than the alkanes. The enthalpy difference Delta H of the LE -> ICT reaction in n-hexane, -11 kJ/mol for FPP4C and -7 kJ/mol for PP4C, is determined by analyzing the temperature dependence of Phi'(ICT)/Phi(LE). Using these data, the energy E(FC,ICT) of the Franck-Condon ground state populated by the ICT emission is calculated, 41 (FPP4C) and 40 kJ/mol (PP4C). These large values for E(FC,ICT) lead to the conclusion that with FPP4C and PP4C, direct ICT excitation, bypassing LE, does not take place. FPP4C has an ICT dipole moment of 15 D, similar to that of PP4C (16 D). Picosecond fluorescence decays allow the determination of the ICT lifetime, from which the radiative rate constant k(f)'(ICT) is derived, with comparable values for FPP4C and PP4C. This shows that an argument for a twisted ICT state of PP4C cannot come from k(f)'(ICT). After correction for the solvent refractive index and the energy of the emission maximum (v) over tilde (max)(ICT), it appears that k(f)'(ICT) is solvent-polarity-independent. Femtosecond transient absorption with FPP4C and PP4C in n-hexane reveals that the ICT state is already nearly fully present at 100 fs after excitation, in rapid equilibrium with LE. In MeCN, the ICT state of FPP4C and PP4C is likewise largely developed at this delay time, and the reaction is limited by dielectric solvent relaxation, which shows that the ICT reaction is ultrafast, at the experimental time limit of 50 fs. PP4C and FPP4C have a similar planar ICT structure, without an appreciable twist of the pyrrole and benzonitrile subgroups. Their crystal structure is compared with calculations for the S-0 ground state."],["dc.description.sponsorship","Hungarian Science Foundation [76278]"],["dc.identifier.doi","10.1021/jp8037413"],["dc.identifier.isi","000258980700006"],["dc.identifier.pmid","18710193"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/53321"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","1089-5639"],["dc.title","Intramolecular charge transfer with the planarized 4-cyanofluorazene and its flexible counterpart 4-cyano-N-phenylpyrrole. Picosecond fluorescence decays and femtosecond excited-state absorption"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]