Transient Photoconductivity in Polyacetylene and Polydiacetylene

1987 ◽  
Vol 109 ◽  
Author(s):  
D. Moses ◽  
S. Phillips ◽  
M. Sinclair ◽  
A. J. Heeger
Keyword(s):  
Quantum Yield ◽  
Conducting Polymers ◽  
Single Crystal ◽  
Conjugated Polymer ◽  
Crystal Form ◽  
Transport Mechanisms ◽  
Polymeric Systems ◽  
Transient Photoconductivity ◽  
Time Regime ◽  
In Trans

ABSTRACTConducting polymers have been found to be rather good photoconductors in the sub-nansecond time regime. The TP measurement is an effective probe for determining carrier photogeneration quantum yield as well as for investigating transport mechanisms. Here, we present a short survey of our results for a few interesting polymeric systems. We start with the trans-(CH)x grown by the Shirakawa method. We then compared the TP results to those obtained from PDA-TS which currently is the only conjugated polymer in single crystal form. From this comparison, we are able to gauge the improvements in the material quality as was demonstrated by recent TP in trans-(CH)x grown by the Naarmann method

scholarly journals Effect of pressure on the crystal structure of L-serine-I and the crystal structure of L-serine-II at 5.4 GPa

2005 ◽  
Vol 61 (1) ◽  
pp. 58-68 ◽  
Author(s):  
Stephen A. Moggach ◽  
David R. Allan ◽  
Carole A. Morrison ◽  
Simon Parsons ◽  
Lindsay Sawyer
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Hydrogen Bonds ◽  
Single Crystal ◽  
Ambient Pressure ◽  
Crystal Form ◽  
Hydroxyl Groups ◽  
Orthorhombic Space Group ◽  
Crystal Forms ◽  
Hydrogen Bonded

The crystal structure of L-serine has been determined at room temperature at pressures between 0.3 and 4.8 GPa. The structure of this phase (hereafter termed L-serine-I), which consists of the molecules in their zwitterionic tautomer, is orthorhombic, space group P212121. The least compressible cell dimension (c), corresponds to chains of head-to-tail NH...carboxylate hydrogen bonds. The most compressible direction is along b, and the pressure-induced distortion in this direction takes the form of closing up voids in the middle of R-type hydrogen-bonded ring motifs. This occurs by a change in the geometry of hydrogen-bonded chains connecting the hydroxyl groups of the —CH2OH side chains. These hydrogen bonds are the longest conventional hydrogen bonds in the system at ambient pressure, having an O...O separation of 2.918 (4) Å and an O...O...O angle of 148.5 (2)°; at 4.8 GPa these parameters are 2.781 (11) and 158.5 (7)°. Elsewhere in the structure one NH...O interaction reaches an N...O separation of 2.691 (13) Å at 4.8 GPa. This is amongst the shortest of this type of interaction to have been observed in an amino acid crystal structure. Above 4.8 GPa the structure undergoes a single-crystal-to-single-crystal phase transition to a hitherto uncharacterized polymorph, which we designate L-serine-II. The OH...OH hydrogen-bonded chains of L-serine-I are replaced in L-serine-II by shorter OH...carboxyl interactions, which have an O...O separation of 2.62 (2) Å. This phase transition occurs via a change from a gauche to an anti conformation of the OH group, and a change in the NCαCO torsion angle from −178.1 (2)° at 4.8 GPa to −156.3 (10)° at 5.4 GPa. Thus, the same topology appears in both crystal forms, which explains why it occurs from one single-crystal form to another. The transition to L-serine-II is also characterized by the closing-up of voids which occur in the centres of other R-type motifs elsewhere in the structure. There is a marked increase in CH...O hydrogen bonding in both phases relative to L-serine-I at ambient pressure.

Emission of a Single Conjugated Polymer Chain Isolated in Its Single Crystal Monomer Matrix

2001 ◽  
Vol 87 (8) ◽  
Author(s):  
T. Guillet ◽  
J. Berréhar ◽  
R. Grousson ◽  
J. Kovensky ◽  
C. Lapersonne-Meyer ◽  
...  
Keyword(s):  
Single Crystal ◽  
Polymer Chain ◽  
Conjugated Polymer

A homoleptic, all-alkynyl-stabilized highly luminescent Au8Ag8cluster with a single crystal X-ray structure

2016 ◽  
Vol 45 (32) ◽  
pp. 12772-12778 ◽  
Author(s):  
Rui Zhang ◽  
Chongyang Zhao ◽  
Xiumin Li ◽  
Zongyao Zhang ◽  
Xicheng Ai ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Single Crystal ◽  
Room Temperature ◽  
X Ray ◽  
Ag Cluster ◽  
Very High

An all-alkynyl-stabilized, intensely luminescent Au–Ag cluster was synthesized and characterized with a very high solution quantum yield at room temperature.

scholarly journals Synthesis and Preliminary Characterization of a PPE-Type Polymer Containing Substituted Fullerenes and Transition Metal Ligation Sites

2015 ◽  
Vol 2015 ◽  
pp. 1-11
Author(s):  
Corinne A. Basinger ◽  
Kaitlin Sullivan ◽  
Sarah Siemer ◽  
Stuart Oehrle ◽  
Keith A. Walters
Keyword(s):  
Transition Metal ◽  
Excited States ◽  
Conjugated Polymer ◽  
Repeat Unit ◽  
Sonogashira Coupling ◽  
Polymeric Systems ◽  
Preliminary Characterization ◽  
Repeat Units ◽  
Future Work

A substituted fullerene was incorporated into a PPE-conjugated polymer repeat unit. This subunit was then polymerized via Sonogashira coupling with other repeat units to create polymeric systems approaching 50 repeat units (based on GPC characterization). Bipyridine ligands were incorporated into some of these repeat units to provide sites for transition metal coordination. Photophysical characterization of the absorption and emission properties of these systems shows excited states located on both the fullerene and aromatic backbone of the polymers that exist in a thermally controlled equilibrium. Future work will explore other substituted polyaromatic systems using similar methodologies.

Direct observation of deuterium migration in crystalline-state reaction by single-crystal neutron diffraction. III. Photoracemization of 1-cyanoethyl cobaloxime complexes

2001 ◽  
Vol 57 (4) ◽  
pp. 551-559 ◽  
Author(s):  
Takashi Ohhara ◽  
Hidehiro Uekusa ◽  
Yuji Ohashi ◽  
Ichiro Tanaka ◽  
Shintaro Kumazawa ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Bond Cleavage ◽  
Cobalt Complexes ◽  
Crystal Form ◽  
Xenon Lamp ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Stereogenic Center ◽  
Cyanoethyl Group

The H atoms bonded to the chiral C atoms (stereogenic center) of the 1-cyanoethyl groups in two cobalt complexes, [(R)-1-cyanoethyl]bis(dimethylglyoximato)(pyridine)cobalt(III) (2) and [(R,S)-1-cyanoethyl]bis(dimethylglyoximato)(piperidine)cobalt(III) (3), were replaced with D atoms, such as Co—C*D(CH3)CN. The crystals of the two cobalt complexes were irradiated with a xenon lamp for 72 h and 27 d, respectively. The unit-cell dimensions were gradually changed with retention of the single-crystal form. The crystal structures after irradiation were determined by neutron diffraction. In each crystal the chiral 1-cyanoethyl group of one of the two crystallographically independent molecules was partly inverted to the opposite configuration, whereas that of the other molecule kept the original configuration. The C*—D bond in the inverted group was completely conserved in the process of the inversion of the chiral alkyl group. This suggests that the inversion of the chiral 1-cyanoethyl group proceeds with the rotation of the cyanoethyl radical after the Co—C bond cleavage by photo-irradiation so that the opposite side of the radical faces the Co atom. This is followed by recombination of the Co—C bond to form the inverted 1-cyanoethyl group.

Transient esr observation of triplet-soliton pairs in a conjugated polymer single crystal

1987 ◽  
Vol 133 (6) ◽  
pp. 482-484 ◽  
Author(s):  
M. Winter ◽  
A. Grupp ◽  
M. Mehring ◽  
H. Sixl
Keyword(s):  
Single Crystal ◽  
Conjugated Polymer
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