Morphology-controllable Fabrication Of Boron-difluoride Complex Micro/Nano-materials And Their Morphology-sensitive Photophysical Properties

In this thesis, a novel phosphorescent organic micro/nano-material composed of boron-difluoride (BF2) complex microcrystal was synthesized. Then, through vapor-solid and solid-phase anion exchange reactions, protonated BF2 complex microcrystals with controllable morphology were obtained, which exhibit morphology induced higher phosphorescence quantum yields (PHQYs) and enhanced near-infrared absorptions. In order to further develop morphology-control method and investigate how morphology influence their properties, a series of BF2 complexes microcrystals with various morphology were fabricated. Our work opens a new direction in developing novel organic micro/nanomaterials and further exploring the effects of morphology on their photophysical properties.1. The BF2 complex (BF2-bipo(1)) organic microcrystal with three-dimensional (3D) prismlike morphology was synthesized from 2,3’-biimidazo[1,2-a]pyridin-2’-one radical (Hbipo-) with BF3-OEt2 in DMF solution. Then protonated BF2 complex (BF2-HbipoCl(1a)) microcrystal with two-dimensional (2D) hexangular flakelike morphology and BF2-HbipoClO4 complex (1b) microcrystal with one-dimensional (1D) rodlike morphology were prepared through morphology-controllable vapor-solid protonation reaction or solid-phase anion exchange reaction. It is demonstrated that the changes in morphology are accompanied by changes in photophysical properties. With 2D hexangular microflake morphology, 1a exhibit higher PHQY(up to 57.5%) and enhanced near-infrared absorption, which should be attributed to the local field enhancement effect induced by the anisotropic microflake structure (morphology effect). Single-crystal structure analyses were conducted to help us to better understand reasons for the formation of the different morphological organic microcrystals. The vapor-solid and solid-phase anion exchange reactions introduced in this work provide useful strategies for the morphology-controllable fabrication of organic microcrystals.2. To further develop morphology-controllable fabrication by solid-phase anion exchange reactions and investigate how morphology influence photophysical properties of organic nano/microcrystal. Anion-substituted BF2 complexes BF2-HbipoX (1c～1e)、BF2-HbipoClO4 (1f)、BF2-HbipoNO3 (1g) BF2-HbipoTFA (1h) were obtained by facile and environmental friendly solid-phase anion exchange reactions. Using anion exchange strategy, various morphological BF2 complex microcrystals were fabricated which the morphological properties are tuned by different anions. Furthermore, methyl-substituted BF2 complexes reveal the effects of the positional isomers of methyl groups on the morphologies. It is interestingly found that solvent also have important influences on the morphologies. Especially, the solvent can even induce unusual globate polyhedron morphology and related red-shift of phosphorescence emission.3. In order to further investigate how morphology-control method influence the properties of other organic radicals, we synthesized three novel triarylmethyl carbocation radical salts, namely bisimidazo[1,2-a]pyridin-2-one-yl(2-pyridyl) methyl carbocation radical salt (1), bisimidazo[1,2-a]pyridin-2-one-yl(3-pyridyl) methyl carbocation radical salt (2), and bisimidazo[1,2-a]pyridin-2-one-yl (4-pyridyl)methyl carbocation radical salt (3). It is noteworthy that, these triarylmethyl carbocation radical salts exhibit positional isomerism induced supramolecular structures and magnetic properties changes, despite their unobtainable uniform morphology. Single-crystal X-ray diffraction analyses reveal that 1,2 and 3 are positional isomers with different one-dimensional (1D) chain structures. Furthermore, these positional isomers exhibit different magnetic susceptibility values at 300 K.1 with 1D double-stranded chains consists of one repetitive unit having four carbocation radical moieties, giving a magnetic susceptibility value of 1.636 emu K Oe-1 mol-1 at 300 K.2 with 1D chains consists of one repetitive unit with two carbocation radical moieties, giving a magnetic susceptibility value of 0.747 emu K Oe-1 mol-1 at 300 K.3 exhibits a magnetic susceptibility value of 0.326 emu K Oe-1 mol-1 for one isolated spin of the carbocation radical.