Multimetallic complexes based on phosphine- and phosphine oxide- appended p-hydroquinones

Presented here, is the work done with a series of binucleating ligands based on phosphine and phosphine oxide appended p-hydroquinones and their reactions towards various metals sources. The long term goal of the project was to produce coordination polymers that would have novel electronic, magnetic, and optical properties which would be of use in the field of molecular electronics. Binucleating ligands contained a p-hydroquinone motif in which various phosphine- and phosphine oxide substituents have been placed in the ortho position relative to each of the hydroxy position were synthesized. A previously published synthetic method for such lugands utilized n-BuLi to form a phenyl lithium intermediate which was quenched with chlorodiphenylphosphine. This technique was also used to produce a ligand with diisopropylphosphine groups. Phosphine ligands, containing the same structural motif, were also generated using LDA as the lithiating agent. This technique was found to be higher yielding. Phosphine chalcogenide ligands were accessed by further oxidizing the low valent phosphorous centers with either hydrogen peroxide or with elemental sulfur. These ligands were characterized using multinuclear NMR, low and high resolution mass spectroscopy, FTIR, and single crystal X-ray diffraction. Their electrochemical properties were explored with cyclic voltammetry. The phosphine appended ligands were used in the synthesis of a several bimetallic complexes. It was found that the ligands readily reacted with NiCp2 and NiCp*2, displacing one of the cyclopentadiene (Cp) or pentamethylcyclopentadiene (Cp*) rings. A cyclopentadiene complexes, containing diisopropylphine, was readily oxidized by[FeCp2]PF6 to give a NMR silent mixed valence complex. Cyclic voltammetry of these complexes showed a number of reversible waves with a large potential separation. The mixed valence compounds also showed a large absorbance band in the NIR region which was assigned to be an intervalence charge transfer. The cyclic voltammetry and NIR spectroscopy suggest that these systems are very capable of efficient metal-to-metal charge transfer. These complexes were characterized by multinuclear NMR, single crystal X-ray diffraction, UV/VIS-NIR spectroscopy and elemental analysis. The phosphine oxide ligands were reacted with a variety of different metal sources but limited success was gained in obtaining single crystals, allowing structural characterization of these compounds. Single crystals were obtained from products generated by reacting the diphenylphosphine oxide ligand with (Bipy)Cu(NO3)2 and Cu(NO3)2. In all cases the ligand had been further oxidized to a 2,5-dihydroxy-1,4-benzoquinone motif. In the reaction between the diphenylphosphine oxide ligand and (Bipy)Cu(NO3)2 it was found that the phosphine oxide moiety was involved with intermolecular coordination leading to the formation of a one-dimensional polymer composed of a series of bimetallic complexes tethered together. When NaSbF6 was present in the reaction with (Bipy)Cu(NO3)2 a unique tetrametallic complex was formed. Here the phospine oxide moiety was oriented so that two bimetallic complexes were bound together. If only Cu(NO3)2 was present, a two-dimensional polymeric sheet was formed where the ligand was present in two different coordination modes. The electronic properties of these complexes remained to be assessed.

DESIGN, SYNTHESIS AND APPLICATIONS OF FLUORESCENT AND ELECTROCHEMICAL PROBES

“Seeing is believing” the proverb well suits for fluorescent imaging probes. Since we can selectively and sensitively visualize small biomolecules, organelles such as lysosomes, neutral molecules, metal ions, anions through cellular imaging, fluorescent probes can help shed light on the physiological and pathophysiological path ways. Since these biomolecules are produced in low concentrations in the biochemical pathways, general analytical techniques either fail to detect or are not sensitive enough to differentiate the relative concentrations. During my Ph.D. study, I exploited synthetic organic techniques to design and synthesize fluorescent probes with desirable properties such as high water solubility, high sensitivity and with varying fluorescent quantum yields. I synthesized a highly water soluble BOIDPY-based turn-on fluorescent probe for endogenous nitric oxide. I also synthesized a series of cell membrane permeable near infrared (NIR) pH activatable fluorescent probes for lysosomal pH sensing. Fluorescent dyes are molecular tools for designing fluorescent bio imaging probes. This prompted me to design and synthesize a hybrid fluorescent dye with a functionalizable chlorine atom and tested the chlorine re-activity for fluorescent probe design. Carbohydrate and protein interactions are key for many biological processes, such as viral and bacterial infections, cell recognition and adhesion, and immune response. Among several analytical techniques aimed to study these interactions, electrochemical bio sensing is more efficient due to its low cost, ease of operation, and possibility for miniaturization. During my Ph.D., I synthesized mannose bearing aniline molecule which is successfully tested as electrochemical bio sensor. A Ferrocene-mannose conjugate with an anchoring group is synthesized, which can be used as a potential electrochemical biosensor.

CHARACTERIZATION OF THE ATMOSPHERIC EFFECTS ON THE TRANSMISSION OF THERMAL RADIATION

Atmospheric scattering plays a crucial rule in degrading the performance of electro optical imaging systems operating in the visible and infra-red spectral bands, and hence limits the quality of the acquired images, either through reduction of contrast or increase of image blur. The exact nature of light scattering by atmospheric media is highly complex and depends on the types, orientations, sizes and distributions of particles constituting these media, as well as wavelengths, polarization states and directions of the propagating radiation. Here we follow the common approach for solving imaging and propagation problems by treating the propagating light through atmospheric media as composed of two main components: a direct (unscattered), and a scattered component. In this work we developed a detailed model of the effects of absorption and scattering by haze and fog atmospheric aerosols on the optical radiation propagating from the object plane to an imaging system, based on the classical theory of EM scattering. This detailed model is then used to compute the average point spread function (PSF) of an imaging system which properly accounts for the effects of the diffraction, scattering, and the appropriate optical power level of both the direct and the scattered radiation arriving at the pupil of the imaging system. Also, the calculated PSF, properly weighted for the energy contributions of the direct and scattered components is used, in combination with a radiometric model, to estimate the average number of the direct and scattered photons detected at the sensor plane, which are then used to calculate the image spectrum signal to- noise ratio (SNR) in the visible near infra-red (NIR) and mid infra-red (MIR) spectral wavelength bands. Reconstruction of images degraded by atmospheric scattering and measurement noise is then performed, up to the limit imposed by the noise effective cutoff spatial frequency of the image spectrum SNR. Key results of this research are as follows: A mathematical model based on Mie scattering theory for how scattering from aerosols affects the overall point spread function (PSF) of an imaging system was developed, coded in MATLAB, and demonstrated. This model along with radiometric theory was used to predict the limiting resolution of an imaging system as a function of the optics, scattering environment, and measurement noise. Finally, image reconstruction algorithms were developed and demonstrated which mitigate the effects of scattering-induced blurring to within the limits imposed by noise.