Luminescent and Charge-Transport Materials for OLEDs

These projects concern the development of new luminescent materials 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).

Research OLEDs

Recent publications:

Adv. Funct. Mater., 2010, 20, 3426-3439; J. Am. Chem. Soc., 2012, 134, 13930-13933; Adv. Mater., 2012, 24, 2922-2928; Adv. Fun. Mater., 2014, 24, 7257-7271; Adv. Funct. Mater., 2014, 24,1911-1927; Appl. Phys. Lett., 2014, 104, 173303; Dalton Trans., 2015, 44, 8433-8443.

 

 

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 categories:

 (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 from between a light coloured state and dark 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.

Photochromic and Photo-Responsive Materials Cover ResearchResearch PhotoChromic

 

Recent publications:

Chem. Eur. J., 2010, 16, 4750-4761; J. Am. Chem. Soc., 2009, 131, 14549-14559; J. Am. Chem. Soc., 2008, 130, 12898-12900; Angew. Chem. Int. Ed. 2010, 49, 8224-8227;  J. Am. Chem. Soc. 2012, 134, 13930−13933; J. Am. Chem. Soc. 2013, 135 , 3407-3410. Angew. Chem. Int. Ed. 2014, 53, 9086-9089.

 

 (2) Within the last few 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.

Research Photoelimination     Research 2

Recent publications:

Angew. Chem. Int. Ed .2013, 52, 4544-4548;  Org. Lett.2014, 16, 616-619;  Angew. Chem. Int. Ed.2015, 54, 5498-5501; Angew.Chem. Int.Ed. 2015, 54, 15074-15078;  Chem. Eur. J. 2015, 21, 13961-13970.

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.

Research hydroborationCover 2 Research

Recent publications:

  Angew. Chem. Int. Ed., 2012, 51, 5671-5674; Org. Lett., 2011, 13, 1226-1229; Angew. Chem. Int. Ed.2015, 54, 5498-5501; Org. Lett.201618, 720-723; Org. Lett.201618, 1626ĘC1629 . 

 

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 to the eye. Research effort in the Wang group 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.

Luminescent materials as chemical sensors

Research

Recent publications:

Inorg. Chem., 2010, 49, 4394-4404; Chem. Eur. J., 2009, 15, 6131-6137; Inorg. Chem., 2009, 48, 3755-3767; J. Am. Chem. Soc., 2007, 129, 7510-7511. Chem. Commun., 2012, 48, 12059-12061; Inorg. Chem., 2014, 53 , 8036 - 8044; Inorg. Chem., 2014, 53, 9751 - 9760

 

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.

 
 
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