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34 results on '"Al-Suti, Mohammed K."'

8. Dicopper(I) Complexes Incorporating Acetylide-Functionalized Pyridinyl-Based Ligands: Synthesis, Structural, and Photovoltaic Studies

Author

Jayapal, Maharaja, primary, Haque, Ashanul, additional, Al-Busaidi, Idris J., additional, Al-Rasbi, Nawal, additional, Al-Suti, Mohammed K., additional, Khan, Muhammad S., additional, Al-Balushi, Rayya, additional, Islam, Shahidul M., additional, Xin, Chenghao, additional, Wu, Wenjun, additional, Wong, Wai-Yeung, additional, Marken, Frank, additional, and Raithby, Paul R., additional

Published
2018
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9. The role of C-H and C-C stretching modes in the intrinsic non-radiative decay of triplet states in a Pt-containing conjugated phenylene ethynylene.

Author

Köhler, Anna, Khan, Amena L. T., Wilson, Joanne S., Dosche, Carsten, Al-Suti, Mohammed K., Shah, Hakikulla H., and Khan, Muhammad S.

Subjects
PHENYLENE compounds, TRIPLET state (Quantum mechanics), EXCITED state chemistry, PHONON emissions, PHOSPHORESCENCE, FRANCK-Condon principle
Abstract

The intrinsic non-radiative decay (internal conversion) from the triplet excited state in phosphorescent dyes can be described by a multi-phonon emission process. Since non-radiative decay of triplet excitons can be a significant process in organic light-emitting diodes, a detailed understanding of this decay mechanism is important if the overall device efficiency is to be controlled. We compare a deuterated Pt(II)-containing phenylene ethynylene with its non-deuterated counterpart in order to investigate which phonon modes control to the non-radiative decay path. We observe that deuteration does not decrease the non-radiative decay rate. A Franck-Condon analysis of the phosphorescence spectra shows that the electronic excitation is coupled strongly to the breathing mode of the phenyl ring and the C≡C carbon stretching modes, while high-energy C-H or C-D stretching modes play an insignificant role. We, therefore, associate the internal conversion process with the carbon-carbon stretching vibrations. [ABSTRACT FROM AUTHOR]

Published
2012
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10. The effect of delocalization on the exchange energy in meta- and para-linked Pt-containing carbazole polymers and monomers.

Author

Zhang, Ning, Hayer, Anna, Al-Suti, Mohammed K., Al-Belushi, Rayya A., Khan, Muhammad S., and Köhler, Anna

Subjects
POLYMERS, MONOMERS, CARBAZOLE, OVERLAP integral, CHROMATOGRAPHIC analysis, EXCITON theory
Abstract

A series of novel platinum-containing carbazole monomers and polymers was synthesized and fully characterized by UV-VIS absorption, luminescence, and photoinduced absorption studies. In these compounds, a carbazole unit is incorporated into the main chain via either a para- or a meta-linkage. We discuss the effects of linkage and polymerization on the energy levels of S1, T1, and Tn. The S1-T1 splitting observed for the meta-linked monomer (0.4 eV) is only half of that in the para-linked monomer (0.8 eV). Upon polymerization, the exchange energy in the para-linked compound reduces, yet still remains larger than in the meta-linked polymer. We attribute the difference in exchange energy to the difference in wave function overlap between electron and hole in these compounds. [ABSTRACT FROM AUTHOR]

Published
2006
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12. Two Is Better than One? Investigating the Effect of Incorporating Re(CO)3Cl Side Chains into Pt(II) Diynes and Polyynes

Author

Haque, Ashanul, Al-Balushi, Rayya, Al-Busaidi, Idris Juma, Al-Rasbi, Nawal K., Al-Bahri, Sumayya, Al-Suti, Mohammed K., Khan, Muhammad S., Abou-Zied, Osama K., Skelton, Jonathan M., and Raithby, Paul R.

Abstract

Pt(II) diynes and polyynes incorporating 5,5′- and 6,6′-disubstituted 2,2′-bipyridines were prepared following conventional Sonogashira and Hagihara dehydrohalogenation reaction protocols. Using Pt(II) dimers and polymers as a rigid-rod backbone, four new heterobimetallic compounds incorporating Re(CO)3Cl as a pendant functionality in the 2,2′-bipyridine core were obtained. The new heterobimetallic Pt–Re compounds were characterized by analytical and spectroscopic techniques. The solid-state structures of a Re(I)-coordinated diterminal alkynyl ligand and a representative model compound were determined by single-crystal X-ray diffraction. Detailed photophysical characterization of the heterobimetallic Pt(II) diynes and polyynes was carried out. We find that the incorporation of the Re(CO)3Cl pendant functionality in the 2,2′-bipyridine-containing main-chain Pt(II) diynes and polyynes has a synergistic effect on the optical properties, red shifting the absorption profile and introducing strong long-wavelength absorptions. The Re(I) moiety also introduces strong emission into the monomeric Pt(II) diyne compounds, whereas this is suppressed in the polyynes. The extent of the synergy depends on the topology of the ligands. Computational modeling was performed to compare the energetic stabilities of the positional isomers and to understand the microscopic nature of the major optical transitions. We find that 5,5′-disubstituted 2,2′-bipyridine systems are better candidates in terms of yield, photophysical properties, and stability than their 6,6′-substituted counterparts. Overall, this work provides an additional synthetic route to control the photophysical properties of metallaynes for a variety of optoelectronic applications.

Published
2021
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14. Experimental and Theoretical Investigation for the Level of Conjugation in Carbazole-Based Precursors and Their Mono-, Di-, and Polynuclear Pt(II) Complexes

Author

Al-Balushi, Rayya A., primary, Haque, Ashanul, additional, Jayapal, Maharaja, additional, Al-Suti, Mohammed K., additional, Husband, John, additional, Khan, Muhammad S., additional, Koentjoro, Olivia F., additional, Molloy, Kieran C., additional, Skelton, Jonathan M., additional, and Raithby, Paul R., additional

Published
2016
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16. Triplet energy transfer in conjugated polymers : I. Experimental investigation of a weakly disordered compound

Author

Devi, Lekshmi Sudha, Al-Suti, Mohammed K., Dosche, Carsten, Khan, Muhammad S., Friend, Richard H., and Köhler, Anna

Subjects
Institut für Chemie
Abstract

Efficient triplet exciton emission has allowed improved operation of organic light-emitting diodes (LEDs). To enhance the device performance, it is necessary to understand what governs the motion of triplet excitons through the organic semiconductor. Here, we have investigated triplet diffusion using a model compound that has weak energetic disorder. The Dexter-type triplet energy transfer is found to be thermally activated down to a transition temperature T- T, below which the transfer rate is only weakly temperature dependent. We show that above the transition temperature, Dexter energy transfer can be described within the framework of Marcus theory. We suggest that below T-T, the nature of the transfer changes from phonon-assisted hopping to quantum-mechanical tunneling. The lower electron-phonon coupling and higher electronic coupling in the polymer compared to the monomer results in an enhanced triplet diffusion rate.

Published
2008

17. Large magnetoresistance in nonmagnetic pi-conjugated semiconductor thin film devices

Author

Mermer, Ö., Veeraraghavan, G., Francis, T. L., Sheng, Y., Nguyen, D. T., Wohlgenannt, M., Köhler, Anna, Al-Suti, Mohammed K., and Khan, Muhammad S.

Subjects
Institut für Physik und Astronomie
Abstract

Following the recent observation of large magnetoresistance at room temperature in polyfluorene sandwich devices, we have performed a comprehensive magnetoresistance study on a set of organic semiconductor sandwich devices made from different pi-conjugated polymers and small molecules. The study includes a range of materials that show greatly different chemical structure, mobility, and spin-orbit coupling strength. We study both hole and electron transporters at temperatures ranging from 10 K to 300 K. We observe large negative or positive magnetoresistance (up to 10% at 300 K and 10 mT) depending on material and device operating conditions. We discuss our results in the framework of known magnetoresistance mechanisms and find that none of the existing models can explain our results.

Published
2005

18. Spectroscopic study of spin-dependent exciton formation rates in pi-conjugated semiconductors : Comparison with electroluminescence techniques

Author

Yang, C., Vardeny, Z. V., Köhler, Anna, Wohlgenannt, M., Al-Suti, Mohammed K., and Khan, Muhammad S.

Subjects
Institut für Physik und Astronomie, Condensed Matter::Strongly Correlated Electrons
Abstract

It has been found in recent measurements that the singlet-to-triplet exciton ratio in organic light-emitting diodes (OLEDs) is larger than expected from spin degeneracy, and that singlet excitons form at a larger rate than triplets. We employed the technique of optically detected magnetic resonance to measure the spin-dependent exciton formation rates in films of a polymer and corresponding monomer, and explore the relation between the formation rates and the actual singlet-to-triplet ratio measured previously in OLEDs. We found that the spin-dependent exciton formation rates can indeed quantitatively explain the observed exciton yields, and that singlet formation rates and yields are significantly enhanced only in polymer OLEDs, but not in OLEDs made from the corresponding monomer

Published
2004

19. Synthesis, characterisation and optical spectroscopy of platinum(II) di-ynes and poly-ynes incorporating condensed aromatic spacers in the backbone

Author

Khan, Muhammad S., Al-Mandhary, Muna R. A., Al-Suti, Mohammed K., Al-Battashi, Fathiya R., Al-Saadi, Sultan, Bjernemose, Jens K., Mahon, Mary F., Chawdhury, Nazia, Yonus, Muhammad, Köhler, Anna, Teat, Simon J., Marseglia, Elizabeth A., Tedesco, Emilio, Feeder, Neil, Ahrens, Birte, and Raithby, Paul R.

Subjects
Institut für Physik und Astronomie
Published
2004

20. New di-ferrocenyl-ethynylpyridinyl triphenylphosphine copper halide complexes and related di-ferricenyl electro-crystallized materials

Author

Shah, Hakikulla H., primary, Al-Balushi, Rayya A., additional, Al-Suti, Mohammed K., additional, Khan, Muhammad S., additional, Marken, Frank, additional, Sudlow, Anna L., additional, Kociok-Köhn, Gabriele, additional, Woodall, Christopher H., additional, Raithby, Paul R., additional, and Molloy, Kieran C., additional

Published
2014
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21. New Multi-Ferrocenyl- and Multi-Ferricenyl- Materials via Coordination-Driven Self-Assembly and via Charge-Driven Electro-Crystallization

Author

Shah, Hakikulla H., primary, Al-Balushi, Rayya A., additional, Al-Suti, Mohammed K., additional, Khan, Muhammad S., additional, Woodall, Christopher H., additional, Sudlow, Anna L., additional, Raithby, Paul R., additional, Kociok-Köhn, Gabriele, additional, Molloy, Kieran C., additional, and Marken, Frank, additional

Published
2013
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22. Long-Range Intramolecular Electronic Communication in Bis(ferrocenylethynyl) Complexes Incorporating Conjugated Heterocyclic Spacers: Synthesis, Crystallography, and Electrochemistry

Author

Shah, Hakikulla H., primary, Al-Balushi, Rayya A., additional, Al-Suti, Mohammed K., additional, Khan, Muhammad S., additional, Woodall, Christopher H., additional, Molloy, Kieran C., additional, Raithby, Paul R., additional, Robinson, Thomas P., additional, Dale, Sara E. C., additional, and Marken, Frank, additional

Published
2013
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23. Synthesis and characterization of platinum(ii) di-ynes and poly-ynes incorporating ethylenedioxythiophene (EDOT) spacers in the backbone

Author

Khan, Muhammad S., primary, Al-Suti, Mohammed K., additional, Shah, Hakkikulla H., additional, Al-Humaimi, Said, additional, Al-Battashi, Fathiya R., additional, Bjernemose, Jens K., additional, Male, Louise, additional, Raithby, Paul R., additional, Zhang, Ning, additional, Köhler, Anna, additional, and Warren, John E., additional

Published
2011
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27. Synthesis, characterisation and optical spectroscopy of platinum(ii) di-ynes and poly-ynes incorporating condensed aromatic spacers in the backbone

Author

Khan, Muhammad S., primary, Al-Mandhary, Muna R. A., additional, Al-Suti, Mohammed K., additional, Al-Battashi, Fathiya R., additional, Al-Saadi, Sultan, additional, Ahrens, Birte, additional, Bjernemose, Jens K., additional, Mahon, Mary F., additional, Raithby, Paul R., additional, Younus, Muhammad, additional, Chawdhury, Nazia, additional, Köhler, Anna, additional, Marseglia, Elizabeth A., additional, Tedesco, Emilio, additional, Feeder, Neil, additional, and Teat, Simon J., additional

Published
2004
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30. Synthesis and characterisation of new acetylide-functionalised aromatic and hetero-aromatic ligands and their dinuclear platinum complexes

Author

Khan, Muhammad S., primary, Al-Suti, Mohammed K., additional, Al-Mandhary, Muna R. A., additional, Ahrens, Birte, additional, Bjernemose, Jens K., additional, Mahon, Mary F., additional, Male, Louise, additional, Raithby, Paul R., additional, Friend, Richard H., additional, Köhler, Anna, additional, and Wilson, Joanne S., additional

Published
2003
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31. Synthesis and optical characterisation of platinum(ii) poly-yne polymers incorporating substituted 1,4-diethynylbenzene derivatives and an investigation of the intermolecular interactions in the diethynylbenzene molecular precursorsElectronic supplementary information (ESI) available: atomic cooordinates for 6 and 7. See http://www.rsc.org/suppdata/nj/b2/b206946f/

Author

Khan, Muhammad S., primary, Al-Mandhary, Muna R. A., additional, Al-Suti, Mohammed K., additional, Corcoran, Timothy C., additional, Al-Mahrooqi, Yaqoub, additional, Attfield, J. Paul, additional, Feeder, Neil, additional, David, William I. F., additional, Shankland, Kenneth, additional, Friend, Richard H., additional, Köhler, Anna, additional, Marseglia, Elisabeth A., additional, Tedesco, Emilio, additional, Tang, Chiu C., additional, Raithby, Paul R., additional, Collings, Jonathan C., additional, Roscoe, Karl P., additional, Batsanov, Andrei S., additional, Stimson, Lorna M., additional, and Marder, Todd B., additional

Published
2002
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32. Structural characterisation of a series of acetylide-functionalised oligopyridines and the synthesis, characterisation and optical spectroscopy of platinum di-ynes and poly-ynes containing oligopyridyl linker groups in the backbone

Author

Khan, Muhammad S., primary, Al-Mandhary, Muna R. A., additional, Al-Suti, Mohammed K., additional, Hisahm, Abdul Khader, additional, Raithby, Paul R., additional, Ahrens, Birte, additional, Mahon, Mary F., additional, Male, Louise, additional, Marseglia, Elisabeth A., additional, Tedesco, Emilio, additional, Friend, Richard H., additional, Köhler, Anna, additional, Feeder, Neil, additional, and Teat, Simon J., additional

Published
2002
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33. Synthesis and optical characterisation of platinum(ii) poly-yne polymers incorporating substituted 1,4-diethynylbenzene derivatives and an investigation of the intermolecular interactions in the diethynylbenzene molecular precursors

Author

Khan, Muhammad S., Al-Mandhary, Muna R. A., Al-Suti, Mohammed K., Corcoran, Timothy C., Al-Mahrooqi, Yaqoub, Attfield, J. Paul, Feeder, Neil, David, William I. F., Shankland, Kenneth, Friend, Richard H., Köhler, Anna, Marseglia, Elisabeth A., Tedesco, Emilio, Tang, Chiu C., Raithby, Paul R., Collings, Jonathan C., Roscoe, Karl P., Batsanov, Andrei S., Stimson, Lorna M., and Marder, Todd B.

Abstract

A series of 1,4-diethynylbenzene (1) derivatives, H–C&z.tbd;C–R–C&z.tbd;C–H with R = C6H3NH2 (2), C6H3F (3), C6H2F2-2,5 (4), C6F4 (5), C6H2(OCH3)2-2,5 (6) and C6H2(OnC8H17)2-2,5 (7) has been synthesised and their crystal structures determined by single crystal (2–5) or powder (6, 7) X-ray diffraction. The C&z.tbd;CH⋯πC&z.tbd;C hydrogen bonds dominating structure 1 are gradually replaced by C&z.tbd;C–H⋯F ones with the increase of fluorination (3 → 5), or completely replaced by C&z.tbd;CH⋯N and NH⋯πC&z.tbd;C bonds in 2, and C&z.tbd;CH⋯O in 6 and 7. The related platinum-based polymers, trans-[–Pt(PnBu3)2–C&z.tbd;C–R–C&z.tbd;C–]n (R = as above and C6H4,) have been prepared and characterised by spectroscopic methods and thermogravimetry, which show that the amino- and methoxy-derivatives have lowest thermal stability while the fluorinated ones exhibit increasing thermal stability with increasing fluorination. Optical spectroscopic measurements reveal that substituents on the aromatic spacer group do not create strong donor–acceptor interactions along the rigid backbone of the organometallic polymers.

Published
2003

34. Two Is Better than One? Investigating the Effect of Incorporating Re(CO) 3 Cl Side Chains into Pt(II) Diynes and Polyynes.

Author

Haque A, Al-Balushi R, Al-Busaidi IJ, Al-Rasbi NK, Al-Bahri S, Al-Suti MK, Khan MS, Abou-Zied OK, Skelton JM, and Raithby PR

Abstract

Pt(II) diynes and polyynes incorporating 5,5'- and 6,6'-disubstituted 2,2'-bipyridines were prepared following conventional Sonogashira and Hagihara dehydrohalogenation reaction protocols. Using Pt(II) dimers and polymers as a rigid-rod backbone, four new heterobimetallic compounds incorporating Re(CO) 3 Cl as a pendant functionality in the 2,2'-bipyridine core were obtained. The new heterobimetallic Pt-Re compounds were characterized by analytical and spectroscopic techniques. The solid-state structures of a Re(I)-coordinated diterminal alkynyl ligand and a representative model compound were determined by single-crystal X-ray diffraction. Detailed photophysical characterization of the heterobimetallic Pt(II) diynes and polyynes was carried out. We find that the incorporation of the Re(CO) 3 Cl pendant functionality in the 2,2'-bipyridine-containing main-chain Pt(II) diynes and polyynes has a synergistic effect on the optical properties, red shifting the absorption profile and introducing strong long-wavelength absorptions. The Re(I) moiety also introduces strong emission into the monomeric Pt(II) diyne compounds, whereas this is suppressed in the polyynes. The extent of the synergy depends on the topology of the ligands. Computational modeling was performed to compare the energetic stabilities of the positional isomers and to understand the microscopic nature of the major optical transitions. We find that 5,5'-disubstituted 2,2'-bipyridine systems are better candidates in terms of yield, photophysical properties, and stability than their 6,6'-substituted counterparts. Overall, this work provides an additional synthetic route to control the photophysical properties of metallaynes for a variety of optoelectronic applications.

Published
2021
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