6 research outputs found
Engineering a light-driven cyanine based molecular rotor to enhance the sensitivity towards a viscous medium.
This article describes the enhanced sensitivity to a viscous medium by a molecular rotor based fluorophore (RBF), TPSI I. The TPSI I molecule is designed in such a way that it consists of a rotor and a fluorophore with a p-rich bridge between them. TPSI I is a light-responsive material in solution as well as in the solid state. The structural design of the molecule allows flexible rotation and photo-induced cis-trans isomerization both in the solid state as well as in solution. These combined attributes of TPSI I are responsible for the ultrasensitive viscosity response of the new material, which was verified through the Fo Ìrster-Hoffmann equation. According to this equation, the derived 'x' value is 1.02 (x is related to the sensitivity) which is the highest among the contemporary reports for RBFs. The facts were evidenced both by experimental as well as theoretical data. The ultrasensitivity towards viscosity was further analyzed in in vitro studies by detecting the subtle changes in the alteration of intracellular viscosity in normal and cancerous cells. An alteration of intracellular viscosity in cells treated with viscosity modula- tors was also confirmed using a previously well-established viscosity measurement technique, dynamic measurement through the piezoelectric patch. Our research offers a detailed mechanism to improve viscosity sensors and an efficient probe for detecting minute changes in intracellular viscosity
A Trapezoidal Octacyanoquinoid Acceptor Forms Solution and Surface Products by Antiparallel Shape Fitting with Conformational Dipole Momentum Switch
A new compound (1) formed by two antiparallelly disposed tetracyano thienoquinoidal units has been synthesized and studied by electrochemistry, UV/Vis-NIR, IR, EPR, and transient spectroscopy. Self-assembly of 1 on a Au(111)
surface has been investigated by scanning tunneling microscopy. Experiments have been rationalized by quantum chemical
calculations. 1 exhibits a unique charge distribution in its anionic form, with a gradient of charge yielding a neat
molecular in-plane electric dipole momentum, which transforms out-of-plane after surface deposition due to twisted!
folded conformational change and to partial charge transfer from Au(111). Intermolecular van der Waals interactions and
antiparallel trapezoidal shape fitting lead to the formation of an optimal dense on Au(111) two-dimensional assembly of 1.
The realization of novel properties emerging upon electronic covalent coupling between chromophores (i.e., bichromophoric systems) is a critical issue for the development of photo- and electrically active systems.[1â3] In this regard, the
relative topology and orientation of the p-subchromophores, such as in A + B type p-systems in Figure 1, with 1D linear
conjugation, 2D parallel conjugation,[4] 3D orthogonal spiroconjugation[5] or 3D conjugation[6] are key factors. On the
other hand, studies of the distribution of the excess of charge in p-conjugated moieties in post-electron transfer events are
central issues in photophysics and photochemistry, in energy storage[7] and in organic electronics.[8] In addition to this
electronic provision, its embedment in different molecular forms is of relevance as these can define unique ways of shape
fitting in supramolecular and surface assemblies. Joint electronic and molecular shape designs thus allow to build
molecular-based synthons in a tailored manner towards new bulk and nano organized materials. (...)Funding for open access charge: Universidad de MĂĄlaga / CBUA. The authors thank the Spanish Ministry of Science, Innovation and Universities MCIU (projects CTQ2017-83531-R, RED2018-102815-T, MAT2017-85089-C2-1-R), Centro de Excelencia Severo Ochoa grants (SEV-2016-0686, SEV2015-0496 and FUNFUTURE CEX2019-000917-S) and the CAM (QUIMTRONIC-CM project Y2018/NMT-4783). We thank MINECO/FEDER of the Spanish Government (projects PGC2018-098533-B-100 and PID2019-109555GB-I00),
the Eusko Jaurlaritza (Basque Government, project PIBA19-0004) and the Junta de AndalucĂa, Spain (UMA18FEDERJA057). We also thank the Research Central Services (SCAI) of the University of MĂĄlaga and the Donostia International Physics Center (DIPC) Computer Center. We thank Dr. Juwon Oh and Prof. Donhgo Kim from the Spectroscopy Laboratory for Functional p-electronic Systems and Department of Chemistry, Yonsei University in Korea for the generous gift of the TRIR and UV/Vis transient absorption spectroscopy data
Intermolecular Interactions and Charge Resonance Contributions to Triplet and Singlet Exciton States of Oligoacene Aggregates
Intermolecular interactions modulate the electro-optical properties of molecular materials and the nature of low-lying exciton states. Molecular materials composed by oligoacenes are extensively investigated for their semiconducting and optoelectronic properties. Here, we analyze the exciton states derived from time-dependent density functional theory (TDDFT) calculations for two oligoacene model aggregates: naphthalene and anthracene dimers. To unravel the role of inter-molecular interactions, a set of diabatic states is selected, chosen to coincide with local (LE) and charge-transfer (CT) excitations within a restricted orbital space including two occupied and two unoccupied orbitals for each molecular monomer. We study energy profiles and disentangle inter-state couplings to disclose the (CT) character of singlet and triplet exciton states and assess the influence of inter-molecular orientation by displacing one molecule with respect to the other along the longitudinal translation coordinate. The analysis shows that (CT) contributions are relevant, although comparably less effective for triplet excitons, and induce a non-negligible mixed character to the low-lying exciton states for eclipsed monomers and for small translational displacements. Such (CT) contributions govern the La/Lb state inversion occurring for the low-lying singlet exciton states of naphthalene dimer and contribute to the switch from H- to J-aggregate type of the strongly allowed Bb transition of both oligoacene aggregates
Remote Electrostatic Repulsion Trigged by Excited State Antiaromaticity Relief as Origin of Photoacidity in an Organic Dye
Photoacids are molecules which become (more) acidic under photoirradiation, and they find valuable applications in organic synthesis and biological chemistry. We herein report a new photoacid, HDMAPAN-(BF4)2, which functions by a different photoacidity mechanism than existing ones. HDMAPAN-(BF4)2, consisting of one dibenzotropylium and one anilinium moiety connected together by a biaryl C-C bond, shows an exceptionally low computed Delta_pKa(hv) (-12.3), which is within the range of superphotoacids. Surprisingly, despite the electronic S0 to S1 transition being located in the dibenzotropylium unit, the photoexcitation affects the acidity of the proton on the anilinium unit. Our computational investigations using TD-DFT reveal that the photoacid is functioning by a new mechanism, in which the excited state antiaromatic character of the dibenzotropylium unit in the S1 state unleashes a local reorganization of the charge distribution, alleviating the destabilizing antiaromatic character. Upon excitation, the positive charge within the dibenzotropylium system is localized on the carbons closest to the anilinium ring, creating an increased electrostatic repulsion against the acidic proton. Placing spacers between the dibenzotropylium and the anilinium moieties gradually reduced the computed Delta_pKa, supporting the electrostatic repulsion between the two ring systems as the main source to the strong photoacidity in HDMAPAN-(BF4)2. Finally, using DFT calculations with point charges, we show that a fractional positive charge indeed destabilizes the anilinium system when it is in close proximity
Gold-promoted biocompatible selenium arylation of small molecules, peptides, and proteins
A low pKa (5.2), high polarizable volume (3.8 Ă
), and proneness to oxidation under ambient conditions make selenocysteine (Sec, U) a unique, natural reactive handle present in most organisms across all domains of life. Sec modification still has untapped potential for site-selective protein modification and probing. Herein we demonstrate the use of a cyclometalated gold(III) compound, [Au(bnpy)Cl2], in the arylation of diselenides of biological significance, with a scope covering small molecule models, peptides, and proteins using a combination of multinuclear NMR (including 77Se NMR), and LC-MS. Diphenyl diselenide (Ph-Se)2 and selenocystine, (Sec)2, were used for reaction optimization. This approach allowed us to demonstrate that an excess of diselenide (Au/Se-Se) and an increasing water percentage in the reaction media enhance both the conversion and kinetics of the C-Se coupling reaction, a combination that makes the reaction biocompatible. The C-Se coupling reaction was also shown to happen for the diselenide analogue of the cyclic peptide vasopressin ((Se-Se)-AVP), and the Bos taurus glutathione peroxidase (GPx1) enzyme in ammonium acetate (2 mM, pH = 7.0). The reaction mechanism, studied by DFT revealed a redox-based mechanism where the C-Se coupling is enabled by the reductive elimination of the cyclometalated Au(III) species into Au(I)
A Trapezoidal Octacyanoquinoid Acceptor Forms Solution & Surface Products by Antiparallel Shape Fitting with Conformational Dipole Momentum Switch
A new compound (1) formed by two antiparallelly disposed tetracyano thienoquinoidal units has been synthesized and studied by electrochemistry, UV/VisâNIR, IR, EPR, and transient spectroscopy. Selfâassembly of 1 on a Au(111) surface has been investigated by scanning tunneling microscopy. Experiments have been rationalized by quantum chemical calculations. 1 exhibits a unique charge distribution in its anionic form, with a gradient of charge yielding a neat molecular inâplane electric dipole momentum, which transforms outâofâplane after surface deposition due to twistedâfolded conformational change and to partial charge transfer from Au(111). Intermolecular van der Waals interactions and antiparallel trapezoidal shape fitting lead to the formation of an optimal dense on Au(111) twoâdimensional assembly of 1