scholarly journals Carbonyl-to-Alkyne Electron Donation Effects in up to 10-nm-Long, Unimolecular Oligo(p-phenylene ethynylenes)

2021 ◽  
Vol 03 (02) ◽  
pp. 337-345
Author(s):  
Sinu C. Rajappan ◽  
Olav Vestrheim ◽  
Mona Sharafi ◽  
Jianing Li ◽  
Severin T. Schneebeli
Keyword(s):  
Absorption Spectrum ◽  
Exponential Growth ◽  
Photophysical Properties ◽  
Rotational Barrier ◽  
Carbonyl Groups ◽  
Conformational Disorder ◽  
Triple Bonds ◽  
Phenylene Ethynylenes ◽  
Electron Donation

We synthesized some of the longest unimolecular oligo(p-phenylene ethynylenes) (OPEs), which are fully substituted with electron-withdrawing ester groups. An iterative convergent/divergent (a.k.a. iterative exponential growth – IEG) strategy based on Sonogashira couplings was utilized to access these sequence-defined macromolecules with up to 16 repeating units and 32 ester substituents. The carbonyl groups of the ester substituents interact with the triple bonds of the OPEs, leading to (i) unusual, angled triple bonds with increased rotational barrier, (ii) enhanced conformational disorder, and (iii) associated broadening of the UV/Vis absorption spectrum. Our results demonstrate that fully air-stable, unimolecular OPEs with ester groups can readily be accessed with IEG chemistry, providing new macromolecular backbones with unique geometrical, conformational, and photophysical properties.

Nanoscale aggregates of porphyrin: red-shifted absorption, enhanced absorbance and phototherapeutic activity

2021 ◽  
Author(s):  
Qihang Wu ◽  
Rui Xia ◽  
Chaonan Li ◽  
Yite Li ◽  
Tingting Sun ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Photophysical Properties ◽  
Nanoscale Aggregates ◽  
Supramolecular Aggregation

Supramolecular aggregation of fluorophores will result in a variable absorption spectrum, which is beneficial for tunning the photophysical properties and improving their functionalities. Herein, ordered aggregates of liposoluble porphyrin molecules...

Novel Highly Potential Initiators for the Two-Photon-Induced Photopolymerization Process

2009 ◽  
Vol 1179 ◽  
Author(s):  
Niklas Pucher ◽  
Valentin Satzinger ◽  
Arnulf Rosspeintner ◽  
Georg Gescheidt ◽  
Volker Schmidt ◽  
...  
Keyword(s):  
Solid Freeform Fabrication ◽  
Photophysical Properties ◽  
Fabrication Process ◽  
Freeform Fabrication ◽  
Structure Activity Relationships ◽  
Two Photon ◽  
Triple Bonds ◽  
Processing Window ◽  
Structure Activity ◽  
Donor And Acceptor

AbstractThe development of new optimized photoinitiators for the two-photon induced photopolymerization (TPIP) is essential in order to obtain high resolutions in this solid freeform fabrication process. Herein, we present the syntheses and characterizations of a series of efficient photoinitiators, comprising of a cross conjugated D-π-A-π-D system. The different donor- and acceptor functionalities of the investigated photoinitiators as well as the synthesis of targeted derivatives containing double and triple bonds in the conjugated backbone allowed the evaluation of structure-activity relationships. The basic photophysical properties as well as the activity and ideal processing window under TPIP conditions were investigated for each initiator and compared with typical commercially available one-photon initiator and with two highly potential initiators well known from literature. These tests figured out that the new chromophores are highly potential even at concentrations down to 0.05 wt%.

Differential quenching of the angular momentum of the B and Q bands of a porphyrin as a result of extended ring π-conjugation

2018 ◽  
Vol 22 (12) ◽  
pp. 1111-1128 ◽  
Author(s):  
Riley W. Hooper ◽  
Angel Zhang ◽  
Dominik Koszelewski ◽  
Jan P. Lewtak ◽  
Beata Koszarna ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Excited State ◽  
Magnetic Circular Dichroism ◽  
Photophysical Properties ◽  
Electronic Effects ◽  
Triple Bonds ◽  
Unique Effect ◽  
Meso Position ◽  
Ring Analysis ◽  
Differential Quenching

A novel porphyrin, whose [Formula: see text]-system has been extended via the presence of two additional carbon–carbon triple bonds on opposite meso-positions and by fusion of a single naphthalene unit simultaneously bridging the third meso-position and the [Formula: see text]-carbon of one of the pyrroles, has been synthesized in good yield. Absorption, magnetic circular dichroism, emission, and theoretical spectra are reported for the fused and unfused trans-naphthalene free base and zinc porphyrins. The fusing of one of the naphthalene moieties results in significant changes to the absorption spectrum and, very unusually, the bridged meso-[Formula: see text]-pyrrole fusion results in quenching of the MCD Faraday pseudo-A term in the porphyrin’s B band (S2). This unique effect was interpreted as resulting from the origin of the electronic structure of the second excited state (the B state). The [Formula: see text] and [Formula: see text] polarizations are completely mixed by the electronic effects of the non-symmetric extended conjugation of the [Formula: see text] ring. Analysis of the origin of the MCD signal indicates that the presence of this novel mixed polarization leads to negligible angular momentum in the important B state. To our knowledge, this is the first report in which the magnetic moment in a porphyrin’s intensely absorbing B band has been quenched while the angular momentum in the Q band, the first excited state, remains as normal. This implies that the photophysical properties of the B state are likely very different than those of the Q state, which has novel and significant implications for applications, especially in non-linear spectroscopy.

Tight binding model of conformational disorder effects on the optical absorption spectrum of polythiophenes

2016 ◽  
Vol 18 (18) ◽  
pp. 12521-12533 ◽  
Author(s):  
Joel H. Bombile ◽  
Michael J. Janik ◽  
Scott T. Milner
Keyword(s):  
Absorption Spectrum ◽  
Optical Absorption ◽  
Optical Absorption Spectrum ◽  
Tight Binding ◽  
Cost Effective ◽  
Tight Binding Model ◽  
Binding Model ◽  
Conformational Disorder ◽  
Disorder Effects ◽  
Conduction Bands

A cost effective model that effectively reproduces the effect of dihedral rotations on the valence and conduction bands of polythiophenes.

Engineering supramolecular photoactive nanomaterials by hydrogen-bonding interactions

2011 ◽  
Vol 83 (4) ◽  
pp. 899-912 ◽  
Author(s):  
K. Yoosaf ◽  
Abdelhalim Belbakra ◽  
Anna Llanes-Pallas ◽  
Davide Bonifazi ◽  
Nicola Armaroli
Keyword(s):  
Photophysical Properties ◽  
Solvent Polarity ◽  
Wide Field ◽  
Force Microscopy ◽  
Anthracene Derivative ◽  
Transmission Electron ◽  
Donor Acceptor ◽  
Phenylene Ethynylenes ◽  
A Charge ◽  
Triple H

The photophysical properties of molecules containing anthracene, pyrene, or phenyleneethynylene chromophores bearing complementary triple H-bonding terminal units, namely, 2,6-di(acetylamino)pyridine (donor–acceptor–donor, DAD) and uracyl (acceptor–donor–acceptor, ADA) have been investigated as a function of solvent polarity. For asymmetric systems, presenting only one H-bonding unit, a solvatochromic effect is found, suggesting a charge-transfer character of the lowest electronic excited state. Systematic absorption and emission studies carried out as a function of temperature show that phenylene-ethynylenes having linear geometry and H-bonding functionalities at both ends undergo reversible self-aggregation in cyclohexane (CHX), leading to the formation of spherical nanoparticles, as evidenced by wide-field fluorescence microscopy (WFM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). A combination of an anthracene derivative bearing only one ADA terminal functionality and a linear phenylene-ethynylene derivative possessing two DAD terminal groups in CHX (2:1 molecular ratio) leads to the formation of vesicular nanostructures. The interaction of linear phenylene-ethynylenes possessing two terminal 2,6-di(acetylamino)pyridine functionalities with that bearing bis uracylic units gives origin to nanofibers, while the assembly of the former with bisuracylic units exhibiting bent geometry leads to the formation of helical nanofibers. The length of these fibers can be controlled by addition of the anthracene derivative having only one uracyl group which effectively blocks the extent of H-bonding, prompting the formation of shorter nanorods.

scholarly journals FLUORESCENCE AND RED SHIFT OF THE PHOTOPHYSICAL PROPERTIES FROM PROTONATED SMALL MOLECULE

2020 ◽  
Vol 5 (1) ◽  
pp. 25-29
Author(s):  
Zakarias Seba Ngara
Keyword(s):  
Absorption Spectrum ◽  
Small Molecule ◽  
Energy Gap ◽  
Photophysical Properties ◽  
Photonic Devices ◽  
Red Shift ◽  
Direct Excitation ◽  
Develop Sensor ◽  
Color Emission ◽  
Film State

In this work, the fluorescence (FL) and bathochromic of the photophysical properties from protonated small molecule in cast film state have been investigated. To realize these purposes, the material of 4’,4’’’’-(1,4-phenylene bis (2,2’:6’,2”-terpyridine) (Phtpy) as a small molecule and  camphorsulfonic acid (CSA) as an acid for protonation was selected. For Phtpy, its maxima absorption is 300 nm and no FL color emission. After CSA solution was added in chlorofom solution of Phtpy, the absorption spectrum of protonated Phtpy is broaden to longer wavelength with two new peaks appear at around 350 and 370 nm. Upon direct excitation at wavelength of 300 nm, the range of FL spectrum of original and protonated Phtpy is from 320 to 580 nm and from 370 to 580 with their maxima FL intensities at 360 and 460 nm. Interestingly, protonated Phtpy emits blue FL color emission. In addition, energy gap of protonated Phtpy is smaller than that of pristine Phtpy. Finally, the FL  and remarkable red shift of absorption and FL spectra of protonated Phtpy will pave the way to develop sensor and other photonic devices with high performances in the ultaviolet region.

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