| Abstract: | 我們合成一系列雙取代芳香環之雜環分子，3,6-disubstituted-1,2,4,5-tetrazine與3,6-disubstituted-pyridazine，及其銥金屬錯合物，Ir(Rdppa)3 (Rdppa = di(R''-phenyl)pyridazine, R''=2-Cl, 3-Cl, 4-Cl, 3-Br, 4-Me)與Ir(pdppa)3 (pdppa = 3,4,6-triphenylpyridazine)，此系列分子活化苯環離去氫原子，與銥(III)金屬離子反應形成triscyclometalated中性化合物。由X-ray的單晶結構可知錯合物的構形為trans-Ir(dppa)3，其未鍵結金屬之苯環與相鄰分子之未鍵結苯環具有π-πstacking作用力，使得分子向不同方向延伸堆疊具高對稱性。錯合物的電子吸收光譜具有配位子之π-π*、1MLCT以及屬於自旋禁阻3MLCT之電子躍遷，錯合物具有不錯的磷光放射，其放光波長介於533 nm( Ir(4Cldppa)3 )至575 nm( Ir(pdppa)3 )間，此系列配位基之LUMO能階分佈於較缺電子的pyridazine環上，而HOMO能階則分佈於電子密度較高的芳香環上，藉由對苯環作拉電子基的修飾將降低HOMO能階，發現放光波長產生藍位移，而弱推電子基(-CH3)對放射波長的影響並不明顯，芳香環的修飾降低LUMO能階，使得放光波長紅位移了20 nm。錯合物吸收光譜與放射光譜之stokes shift值均小於100 nm，因此推測這一系列銥錯合物之磷光放射主要源自於3MLCT激發態所貢獻。錯合物的激發態生命期介於0.91 µs( Ir(3Brdppa)3 )至2.9 µs( Ir(4Medppa)3 )間，量子產率最高為Ir(4Cldppa)3之0.429，最低為Ir(dppa)3之0.069。錯合物均具有一可逆的氧化還原峰，苯環有拉電子基的取代，將有效地提高其氧化電位，推電子基之取代則發現其氧化電位降低，由於錯合物之氧化發生於銥中心金屬與苯環間，是故在pyridazine環上苯環的修飾對錯合物的氧化電位並無明顯的影響。放光波長的紅藍位移趨勢取決於淨能隙的變化，當拉電子基的取代，使得HOMO下降的程度大於LUMO，將造成淨能隙增加而使放光波長產生藍位移。由3,6-disubstituted-1,2,4,5-tetrazine衍生得一系列新的H形結構分子，1,4-bis(3,6-di-R"-pyridazin-4-yl)benzene (R"= phenyl、3-chlorophenyl與3-bromophenyl)，X-ray的單晶結構發現1,4-bis(3,6-diphenylpyridazin-4-yl)-benzene分子間具有π-π stacking作用力使得分子交錯堆疊形成孔狀結構，孔徑約6.3 Å x 6.9 Å。3,6-bis(2-hydroxyphenyl)-1,2,4,5-tetrazine (H2boptz)、3,6-bis(2-hydroxyphenyl)pyridazine (H2boppa)與3,5-bis(2-hydroxyphenyl)-1,3,4-oxadiazole (H2bopoa)為新的一系列具有雙苯酚取代之雜環分子，兩苯酚之OH與中間雜環之氮原子均具有氫鍵作用力，使得分子之去質子化較為不易，H2boptz之pKa值為12.7。
The photophysical property of tris-cyclometalated complexes of Ir(III) make them useful for several photonic applications. The attraction of these complexes for such applications comes from their long excited-state lifetime and high luminescent efficiencies. The Synthesis, structure, electrochemistry, and photophysics of the tris-cyclometalated Ir(III) complexes are reported. Reaction of the Ir(acetylacetonate)3 with 3,6-disubstituted-pyridazine (Rdppa, 3,6-di(R’-phenyl)pyridazine, R’=2-Cl, 3Cl, 4-Cl, 3-Br, 4-Me) and 3,4,6-triphenylpyridazine (pdppa) ligands forms the present compounds. The Ir-C and Ir-N bonds with trans configuration is observed for the phenylpyridazine-based complexes. The compounds have intense absorption bands in the UV region assigned into π-π＊ transitions and a weaker MLCT transition that extend to the visible region. The tris-cyclometalated Ir(III) complexes exhibit intense emission at room temperature, with emission characteristic of phosphorescence from a 3MLCT triplet state. The complexes show reversible reduction-oxidation process. The substitution of electron-withdrawing group at phenyl ring resulted in the hypsochromic shift in the emission wavelength since lower HOMO. Electronegative nitrogen and enlarging the π-conjugation exert bathochromic shift on the emission wavelength since lower LUMO.
A microporous material constructed by π-π interaction of a twisted H-shape poly-aromatic molecule, 1,4-bis(3,6-diphenylpyridazin-4-yl)benzene was synthesized by the reaction of 1,4-diacetylbenzene and 3,6-diphenyl-1,2,4,5tetrazine. The intermolecular distances between the various aromatic rings are within the range of 3.4~3.7 Å which indicate the intermolecular π-π stacking interaction. Hexagonal channels with pore width 6.3 Å x 6.9 Å along the c axis were observed. Interstitial water and MeOH molecules were located within each porous channel.
3,6-disubstituted-1,2,4,5-tetrazine moieties have become popular as efficient electronic spacers in dinuclear and polynuclear systems, due to the fact that the tetrazine-based low-lying π* orbital conveys strong π-accepting characteristics, leading to excellent electronic communication between the metal termini. A serial of diphenolate ligands, 3,6-bis(2-hydroxyphenyl)-1,2,4,5-tetrazine (H2boptz), 3,6-bis(2-hydroxyphenyl) pyridazine (H2boppa) and 3,5-bis(2-hydroxyphenyl)-1,3,4-oxadiazole (H2bopoa) were synthesized and characterized, and the ligand H2boptz contain phenolate donors and a central tetrazine π-acceptor function. The pKa value of H2boptz is 12.7. |
