Research Projects
The Dolinar group specializes in the development of new, magnetically interesting compounds, specifically in the fields of MRI contrast agents and single molecule magnetism.
Single Molecule Magnets
Single Molecule Magnets (SMMs) are molecular compounds that exhibit magnetic memory and have the potential to be utilized as magnetic bits in next generation information storage devices. SMMs are much smaller than the magnetic bits currently used in commercially available hard drives. Thus, SMMs have the potential to greatly improve storage density of information storage devices. In such molecules, magnetic anisotropy gives rise to a thermal barrier to magnetic relaxation, resulting in their magnetic memory behavior Current state of the art SMMs only exhibit magnet memory at cryogenic temperatures (< 80 K), limiting their commercial viability. This limitation arises largely from magnetic relaxation phenomena such as quantum tunneling of magnetization (QTM), which serves to circumvent the thermal barrier.​
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Research in the Dolinar lab focuses on low-coordinate transition metal SMMs. Magnetic anisotropy, a key property for SMMs, can be generated in transition metals by using bulky ligands to limit coordination about the metal center. This low-coordination environment can lead to unquenched orbital angular momentum that results in substantial anisotropy. Two-coordinate transition metal complexes are some of the best motifs to generate extremely high axial anisotropy.
Redox Switchable Gd MRI Contrast Agents
Development of MRI contrast agents that respond to the different chemical environments present in various tissues and cells remains a challenge for synthetic chemists. Strategies that have been employed to address this problem include altering the substituents on the ligand in order to tune where the MRI agent localizes within the body as well as the development of pH and redox switchable compounds. In redox-switchable MRI contrast agents, different levels of oxygen content and reactive oxygen species (ROS) present in cells leads to oxidation or reduction of the contrast agent, altering its magnetic behavior and leading to different degrees of contrast in the MRI image.​
The seven unpaired electrons and magnetic isotropy of Gd(III) ions makes them for exceptionally useful as MRI contrast agents. While Gd(III) itself is not redox active in vivo, we can design Gd(III) compounds that posses a redox active moiety. These groups can undergo a redox event in the presence of ROS in the cell altering the magnetic response of the MRI contrast agent, ultimately allowing the oxygen concentration of cells to be probed.
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Blue Organic Light Emitting Diodes (OLEDs)
Organic Light Emitting Diodes (OLEDs) are used in applications such as lighting, phototherapy, and electronic displays. Unlike the LED displays commercially available, an OLED display does not require a rigid backlight, leaving you with a flexible display with more color contrast. OLEDs are also more biodegradable compared to LEDs, leading them to be a more environmentally friendly synthetic target. OLED devices have red, green and blue emitters, of which the blue emitters are the limitation currently. When electricity is applied in a device, the emitting material will absorb that energy which promotes it to an excited state. When the emitter relaxes back to the ground state, the radiative energy released corresponds to the color that is emitted. Blue, being at a low wavelength, is the highest energy part of the OLED device. This high energy state has proven detrimental in synthesizing a stable true-blue emitter that is efficient enough for commercial use.
First generation blue OLEDs are fluorescent emitters which have high color control and operational lifetimes, but they only have 25% theoretical efficiency. Second generation blue OLEDs are phosphorescent emitters which have a theoretical 100% efficiency but have low operational lifetimes and subpar color control. Third generation, and where the research lies, are thermally assisted delayed fluorescence (TADF) blue emitters. TADF emitters have a theoretical 100% efficiency, long operational lifetimes, and high color control. It has been shown that making an orthogonal donor/acceptor pair, introducing spin-orbit couple into the system, and minimizing vibrations within the system can allow TADF to occur.
Our group aims to make efficient blue emitters using various carbazole derivatives with varying soft metals.
Thermally Assisted Delayed Fluorescence
Prompt Fluorescence
Delayed Fluorescence
ISC
RISC
100% efficiency