Synthesis of thienyl-substituted BODIPY dyes towards metal ion sensing

Abstract

In chapter 1, to explore the characteristics of potential fluorescent probes new 5-thienyl dipyrromethene derivatives have been prepared. 5-(2-thienyl)- ($\textbf{1a}$), 5-(3-thienyl)- ($\textbf{1b}$), and 5-(3-(2,5-dibromothienyl))-dipyrromethane ($\textbf{1c}$), were oxidized with DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) separately to give the corresponding dipyrrins $\textbf{2a-2c}$. These were subsequently treated with $F_3B \cdot OEt_2$ to afford the respective N,N’-difluoroboryl-5-(thienyl)dipyrrin compounds, 3a-3c. Significant fluorescence signal enhancement is achieved with $\textbf{3a-3c}$ over $\textbf{2a-2c}$. An X-ray diffraction study of $\textbf{3a}$ was performed (orthorhombic, $P2_12_12_1$, a = 10.684(10) $\AA$, b = 15.208(13) $\AA$, c = 7.256(6) $\AA$, V = 1179.0(17) $\AA^3$, Z = 4, R1 = 0.0428, wR2 = 0.0686) and its geometry was studied by way of DFT (Gaussian 03; $B3LYP/6-31G^*$). Theoretical modeling of $\textbf{2a}$ demonstrated that the [N-H‥‥N] interaction is favored by ca. 10 kcal/mol, whereas [N-H‥‥S] bonding is sterically unattainable. In chapter 2, four novel tetra-thienyl-substituted boron-dipyrrin (BODIPY-type) complexes, 3-(R’)-4,4-di(R’)-8-R-4-bora-3a,4a-diaza-s-indacene ($\textbf{4a}$: R = 2-T, R’ = 2-T; $\textbf{4b}$: R = 2-T, R’ = 3-T; $\textbf{5a}$: R = 3-T, R’ = 2-T; $\textbf{5b}$: R = 3-T, R’ = 3-T. T = thienyl) have been prepared and fully characterized to explore patterns of stoichiometric $M^{n+}$ recognition in solution. Compounds $\textbf{4a}$ and $\textbf{4b}$ bear a neutral “scorpionate”_like [SSS] tridentate binding pocket. Extensive NMR, and UV-vis spectroscopic studies were performed on $\textbf{4a-5b; 5a, 4b,}$ and $\textbf{5b}$ were structurally characterized. The $\phi_F$ values for $\textbf{4a-5b}$ all decrease compared to the $BF_2$-containing parent molecules. Upon treatment with metal ion ($Ca^{2+}, Cs^+, Mn^{2+}, Co^{2+}, Cu^{2+}, Ag^+, Zn^{2+}, Cd^{2+}, Hg^{2+}, Pb^{2+}$) perchlorate salts, th...