An unsymmetrical guanidine-cyclopropenimine proton sponge DAGUN andt he relatedB F 2-chelate DAGBO are reported. Insight into the structural, electronic, bonding and photophysical properties of these two molecules are presented.J oint experimental and theoretical studies reveal the protonated form of DAGUN possessesa ni ntramolecular N•••HÀNh ydrogen bond which affords ah igh experimental pK BH + of 26.6 (computed = 26.3). Photophysical studies show that in solution DAGUN displays ag reen emission at 534 nm, with al arge Stokess hift of 235 nm (14,718 cm À1). In contrast, the conjugate acid DAGUN-H + is only weakly emis-sive due to attenuated intramolecular charge transfer.X-ray diffraction studies revealt hat DAGBO contains as table tetracoordinate boronium cation, reminiscent of the well-established BODIPY family of dyes. In solution, DAGBOe xhibits a strong blue emission at 450 nm coupled with al arge Stokes shift (Dl = 158 nm, Dn = 11,957 cm À1)a nd quantum yield of 62 %, upon excitation at 293 nm. DAGBO sets the stage as the first entry into an ew class of boron-difluoride diaminonaphthalenes (BOFDANs)t hat represent highlyf luorescent and tunable next-generation dyes with future promise for biosensing and bioimaging applications.

The synthesis of cyclopropenium-substituted amino compounds and analysis of their photophysical properties is described. Systematic structural modifications of these derivatives lead to measurable and predictable changes in molar extinction coefficients, quantum yields, and Stokes shifts. Using time-dependent density functional theory (TD-DFT) calculations, the origin of these trends was traced to internal charge transfer (ICT) coupled with ensuing structural reorganization for select naphthalene functionalized derivatives. Associated with this structural reorganization was an inward gearing of the cyclopropenium ring and twisting of the peri-NMe group into coplanarity with the naphthalene ring system. Further, reinforcement of an intramolecular H-bond (IMHB) in the excited state of these derivatives alludes to the importance of photoinduced H-bonding in this new class of cyclopropenium based fluorophores.

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Stereoselective synthesis of zuclomiphene was developed using nickel-catalyzed addition of 4-fluorophenylmagnesium bromide to 1,2-diphenylacetylene, followed by quenching with a chlorinating reagent. Since the aryl fluoride addition and chlorination reactions occur consecutively in one pot, the cis orientation of the two phenyl groups of 1,2-diphenylacetylene is conserved, leading to the highly selective synthesis of zuclomiphene. The use of the Grignard reagent resulted in the presence of bromide ions in the reaction mixture, which led to the formation of the bromo-analog of zuclomiphene. Alternative routes were then explored to overcome this issue to yield high-purity zuclomiphene.

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