Exploiting chemistry and molecular systems for quantum information science.

The power of chemistry to prepare new molecules and materials has driven the quest for new approaches to solve problems having global societal impact, such as in renewable energy, healthcare and information science. In the latter case, the intrinsic quantum nature of the electronic, nuclear and spin degrees of freedom in molecules offers intriguing new possibilities to advance the emerging field of quantum information science. In this Perspective, which resulted from discussions by the co-authors at a US Department of Energy workshop held in November 2018, we discuss how chemical systems and reactions can impact quantum computing, communication and sensing.

Antioxidant Sensing by Spiropyrans: Substituent Effects and NMR Spectroscopic Studies.

The development of stimuli-responsive small molecules for probing biologically active antioxidants such as glutathione (GSH) has important ramifications in the detection of oxidative stress. An ideal sensor for biological applications should exhibit sufficient sensitivity and selectivity for detection at physiological concentrations and be reversible to allow continuous and dynamic monitoring of antioxidant levels. Designing a suitable sensor thus requires a detailed understanding of activation properties and mechanism of action.

Opto-Spintronics: Photoisomerization-Induced Spin State Switching at 300 K in Photochrome Cobalt-Dioxolene Thin Films.

Controllable quantum systems are under active investigation for quantum computing, secure information processing, and nonvolatile memory. The optical manipulation of spin quantum states provides an important strategy for quantum control with both temporal and spatial resolution. Challenges in increasing the lifetime of photoinduced magnetic states at T > 200 K have hindered progress toward utilizing photomagnetic materials in quantum device architectures.

Visible light photoswitching of conjugated polymer nanoparticle fluorescence.

Conjugated polymer nanoparticles doped with a reverse photochromic dye exhibit highly quenched fluorescence that can be reversibly activated by controlling the form of the photochrome with visible light.

Modulating short wavelength fluorescence with long wavelength light.

Two molecules in which the intensity of shorter-wavelength fluorescence from a strong fluorophore is modulated by longer-wavelength irradiation of an attached merocyanine-spirooxazine reverse photochromic moiety have been synthesized and studied. This unusual fluorescence behavior is the result of quenching of fluorophore fluorescence by the thermally stable, open, zwitterionic form of the spirooxazine, whereas the photogenerated closed, spirocyclic form has no effect on the fluorophore excited state. The population ratio of the closed and open forms of the spirooxazine is controlled by the intensity of the longer-wavelength modulated light.

Determining the magnitude and direction of photoinduced ligand field switching in photochromic metal-organic complexes: molybdenum-tetracarbonyl spirooxazine complexes.

The ability to optically switch or tune the intrinsic properties of transition metals (e.g., redox potentials, emission/absorption energies, and spin states) with photochromic metal-ligand complexes is an important strategy for developing "smart" materials.

Ferromagnetic spin-delocalized electron donors for multifunctional materials: π-conjugated benzotriazinyl radicals.

We have developed new synthetic methodology for benzotriazinyl radicals that exhibit spin delocalization, low oxidation potentials, and ferromagnetic interactions in the solid state via π-π interactions, making them promising candidates for multifunctional magnetic materials.

A solution- and solid-state investigation of medium effects on charge separation in metastable photomerocyanines.

The effects of solution-state dielectric and intermolecular interactions on the degree of charge separation in metastable spirooxazine photomerocyanines (PMCs) is investigated. We report the first X-ray diffraction (XRD) analyses of an open form, a metastable photomerocyanine, of the spirooxazine class of photochromic molecules in two derivatives: spiro[azahomoadamantane-isoquinolinoxazine] (1) and spiro[azahomoadamantane-phenanthrolinoxazine] (2). Using the results of XRD analysis of the open photomerocyanine forms, in conjunction with computation, solvatochromism, and solution NMR studies, we have investigated the effect of the medium on the ground-state structure of these photomerocyanines.

Incorporating optical bistability into a magnetically bistable system: a photochromic redox isomeric complex.

A photochromic cobalt-bis(dioxolene)spirooxazine metal complex has been synthesized which exhibits both photochromic and redox-active behavior, providing a potentially powerful approach to the development of optically induced changes in redox, magnetic, or optical properties of a metal center.

Synthesis and characterization of ruthenium and rhenium nucleosides.

We report the synthesis and characterization of new ruthenium and rhenium nucleosides [Ru(tolyl-acac)2(IMPy)-T] (tolyl-acac=di(p-methylbenzonatemethane), IMPy=2'-iminomethylpyridine, T=thymidine) (5) and [Re(CO)3(IMPy)-T]Cl (9), respectively. Structural analysis of 9 shows that the incorporation of this metal complex causes minimal perturbation to the sugar backbone and the nucleobase. Eletrochemical (5, E1/2=0.

Synthesis of neutral spin-delocalized electron acceptors for multifunctional materials.

A new synthetic route to stable spin-delocalized radicals, annelated nitronyl nitroxides, has been developed on the basis of the condensation of benzofuroxan with aryl nitrones. The electronic structure of the resulting radicals was investigated through absorption spectroscopy, EPR, electrochemistry, and computation (DFT-UB3LYP). The annelated radicals exhibit electronic transitions in the near IR (850-900 nm) and are excellent electron acceptors (E(red) approximately 0.

Photochromism of a spirooxazine in the single crystalline phase.

The single crystals of a closed form spirooxazine spiro[azahomoadamantane-isoquinolinoxazine] were found for the first time to undergo photocoloration processes consistent with photochromism in the single crystalline phase.

Tunable photochromism of spirooxazines via metal coordination.

Through the incorporation of a phenanthroline ligand into the oxazine moiety of photochromic spirooxazines, a series of photochromic spirooxazine-phenanthroline metal complexes have been synthesized, resulting in tunable and significantly increased photoresponsivities. Such systems are of interest for the investigation of multifunctional photochromic materials. These novel metal complexes retain their photochromic activity in the complexed state, leading to ligand binding in both the spirooxazine and the photomerocyanine forms during the photoconversion.

5' modification of duplex DNA with a ruthenium electron donor-acceptor pair using solid-phase DNA synthesis.

Incorporation of metalated nucleosides into DNA through covalent modification is crucial to measurement of thermal electron-transfer rates and the dependence of these rates with structure, distance, and position. Here, we report the first synthesis of an electron donor-acceptor pair of 5' metallonucleosides and their subsequent incorporation into oligonucleotides using solid-phase DNA synthesis techniques. Large-scale syntheses of metal-containing oligonucleotides are achieved using 5' modified phosporamidites containing [Ru(acac)(2)(IMPy)](2+) (acac is acetylacetonato; IMPy is 2'-iminomethylpyridyl-2'-deoxyuridine) (3) and [Ru(bpy)(2)(IMPy)](2+) (bpy is 2,2'-bipyridine; IMPy is 2'-iminomethylpyridyl-2'-deoxyuridine) (4).