Luminescent and Charge-Transport Materials for OLEDs
These projects concern the development of new materials with luminescent and/or thermally activated delayed fluorescence (TADF) properties for use as emissive or bifunctional emissive/charge transport materials in organic electronic devices. Research involves the design and preparation of novel materials including main-group embedded heterocycles or organoboron-functionalized transition metal complexes with high emission efficiencies, tunable colours, improved charge-transport, and superior film-forming properties. Synthesis involves extensive work in both organic and organometallic chemistry, making use of metal-catalyzed C-C bond forming and metal-halogen exchange reactions, as well as protocols for introducing metal centers into functional materials. Recent efforts have focused on preparing stable blue phosphorescent emitters based on organoplatinum and are carried out in collaboration with Professors Zheng-Hong Lu (University of Toronto) and Yue Wang (Jilin University, Changchun, China).
- A. John, M. Bolte, H.-W. Lerner, G. Meng, S. Wang, T. Peng,* M. Wagner,* “Doubly boron-doped pentacenes as emitters for OLEDs”, J. Mater. Chem. C., 2018, 6, 10881-10887. DOI: 10.1039/C8TC03954B
- Deng-Tao Yang, Tomoya Nakamura, Zhe-chang He, Xiang Wang, Atsushi Wakamiya, Tai Peng, Suning Wang, "Doping Polycyclic Arenes with Nitrogen-Boron-Nitrogen (NBN) Units", Org. Lett., 2018, 20, 6741–6745, DOI: 10.1021/acs.orglett.8b02850
Photochromic and Photo-Responsive Materials
Photochromic/photo-responsive materials have many important applications
including memory devices/switches, smart windows, and reactivity/molecular shape
control. Our research within this area typically focuses on the photochemical
reactivity of four-coordinated organoboron species and falls into one of two
(1) Several years ago, our group discovered a new class of photochromic
materials based on sterically hindered four-coordinated organoboron
compounds. These materials are capable of switching between a light-coloured state and
a dark-coloured state following the application of either UV light or
heat. More recently, these types of systems have shown an impressive amount of
photochemical diversity depending on the specific framework surrounding the
boron center. Ongoing efforts are focused on establishing a thorough mechanistic
understanding of these transformations, as well as the development of new ligand
frameworks in the hopes of generating new types of photo- or thermal reactivity.
(1) Several years ago, our group discovered a new class of photochromic materials based on sterically hindered four-coordinated organoboron compounds. These materials are capable of switching between a light-coloured state and a dark-coloured state following the application of either UV light or heat. More recently, these types of systems have shown an impressive amount of photochemical diversity depending on the specific framework surrounding the boron center. Ongoing efforts are focused on establishing a thorough mechanistic understanding of these transformations, as well as the development of new ligand frameworks in the hopes of generating new types of photo- or thermal reactivity.
Zhe-Chang He, Soren K. Mellerup, Lijie Liu, Dr. Xiang Wang, Caitlin Dao, Prof. Dr. Suning Wang, "Reversible Photoisomerization from Borepin to Boratanorcaradiene and Double Aryl Migration from Boron to Carbon", Angewandte Chemie, 2019, DOI: 10.1002/anie.201902231
Cally Li, Soren K. Mellerup, Xiang Wang, and Suning Wang, "Accessing Two-Stage Regioselective Photoisomerization in Unsymmetrical N,C-Chelate Organoboron Compounds: Reactivity of B(ppz)(Mes)Ar", Organometallics, 2018 DOI: 10.1021/acs.organomet.8b00598
Controlling Isomerization Selectivity in Chiral, Photochromic N,C-Chelate Organoboron Systems with Extended ¦Ð-Conjugation", J. Org. Chem., 2018, DOI: , " 10.1021/acs.joc.8b01856
(2) In recent years, we have established a new photoelimination reaction involving B,N-heterocyles upon the exposure to UV light. This unprecedented reactivity is highly unusual as it involves the breaking of both a C-H and B-C bond, ultimately leading to the formation of B,N-embedded naphthalene derivatives which would be extremely difficult to prepare by traditional synthetic methods. Further studies have shown that both heat and electricity (excitons generated within OLEDs) can also be used to drive this transformation, allowing for the in situ generation of new B,N-doped arenes within polymer matrices and OLEDs. This strategy offers an attractive alternative to the direct preparation of such polycyclic systems, as the precursor species tend to be much more readily processable.
- Yong-gang Shi, Xiang Wang, Nan Wang, Tai Peng, and Suning Wang "Influence of Extended Conjugation on Photophysical/Electronic Properties and Photoelimination of BN-Heterocycles" Organometallics, 2017, DOI: 10.1021/acs.organomet.7b00290
Reactivity of Organoboron-Containing Compounds
In addition to the photoresponsive behaviour of four-coordinated organoboron compounds, we have also observed unusual chemical reactivity of such systems due to the unique electronic contribution of the organoboron functionality. This cooperativity of an organoboron group with main group elements or transition metal ions provides an interesting platform to explore new types of chemical transformations. Current projects in this area concern new types of hydroboration chemistry (1,1-hydroboration, catalyst-free trans-hydroboration, etc.), as well as the study of their chemical bond cleavage and formation processes.
- K. Yuan, X. Wang, S. Wang*, "Cascade Dehydrogenative Hydroboration for the Synthesis of Azaborabenzofulvenes", Org. Lett. 2018, DOI: 10.1021/acs.orglett.8b00363
- D.-T. Yang, S. K. Mellerup, X. Wang, J.-S. Lu, S. Wang, "Reversible 1,1-Hydroboration: Boryl Insertion into a C-N Bond and Competitive Elimination of HBR2 or R-H" Angewandte Chemie International Edition 2015, 54, 5498-5501
Luminescent Materials as Chemical Sensors
Fluorescent and phosphorescent compounds have great potential as chemical sensors, as they can provide a sensitive and selective response to an analyte that is observable. The Wang group's research effort in this area is currently directed towards: i) the development of luminescent triarylboranes for the selective detection of fluoride ions, ii) synthesis of polypyridyl- and hydroxyquinoline-based materials for the detection of Zn2+, and iii) the preparation of vapour-sensitive luminescent solids for the detection of organic vapours. Projects in this area involve organic and organometallic synthesis, as well as characterization of the response of new materials to the analytes of interest.
Hai-Jun Li, Soren K. Mellerup, Xiang Wang, and Suning Wang, "D−π–A Triarylboranes as Reversible Fluorescent Probes for CO2 and Temperature", Organic Letters, 2019, 21 (8), 2838-2842, DOI: 10.1021/acs.orglett.9b00831
Lijie Liu, Xiang Wang, Faraz Hussain, Chao Zeng, Bowen Wang, Zechen Li, Igor Kozin, Suning Wang*, “Multi-responsive Tetradentate Phosphorescent Metal Complexes as Highly Sensitive and Robust Luminescent Oxygen Sensors: Pd(II) versus Pt(II) and 1,2,3-Triazolyl versus 1,2,4-Triazolyl”, ACS Appl. Mater. Interfaces, 2019. DOI: 10.1021/acsami.9b02023
C. Sun, N. Wang, T. Peng, X. Ying, S. Wang, P. Chen*, “BN-Functionalized Benzotrithiophene-Based Azaborines: Synthesis, Structures, and Anion Binding Properties”, Inorg. Chem., 2019. DOI: 10.1021/acs.inorgchem.8b03579
H. Li, S. K. Mellerup, X. Wang, S. Wang, " Impact of Intramolecular H bond and n-π* interactions on photophysical and CO2 sensing properties of laterally appended D-π-A triarylboron compounds", Tetrahedron, 2018, 75, 809-816, DOI: 10.1016/j.tet.2018.12.032
Charge-Transport Materials for Organic Solar Cells
Photovoltaic devices based on organic materials and semiconductor nanoparticles are an attractive and relatively new class of solar cells that have the potential for simple fabrication at a fraction of the cost of their inorganic counterparts. Research in the Wang group concerns the development of new ligands to act as charge-transporting surfactants for the semiconductor nanoparticles employed in these cells, to better facilitate charge separation and the harvesting of light energy. Work involves organic synthesis for the preparation of new ligands, as well as inorganic methods for the preparation of semiconductor nanoparticles. New materials are tested at the National Research Council Laboratories in collaboration with Dr. Ye Tao's team.
M. Hesari, K. N. Swanick, J.-S. Lu, R. Whyte, S. Wang, Z. Ding, "Highly Efficient Dual-Color Electrochemiluminescence from BODIPY-Capped PbS Nanocrystals " J. Am. Chem. Soc., 2015, 137, pp 11266-11269.
M. Hesari, J.-s. Lu, S. Wang, Z. Ding, "Efficient electrochemiluminescence of a boron-dipyrromethene (BODIPY) dye" Chemical Commun., 2015, 51, 1081-1084.
Jia-sheng Lu, Huiying Fu, Yanguang Zhang, Zygmunt J. Jakubek, Ye Tao, and Suning Wang. "A Dual Emissive BODIPY Dye and Its Use in Functionalizing Highly Monodispersed PbS Nanoparticles." Angew. Chem. Int. Ed., 2011, 50, 11658-11662