Akademik Veri Yönetim Sistemi
JOURNAL OF MOLECULAR STRUCTURE, cilt.1310, 2024 (SCI-Expanded)
Here, new symmetrical diimines D-1 and D-2 were prepared by the condensation reaction of o-vanillin with 2-nitro-p-phenylenediamine or 4-nitro-o-phenylenediamine, respectively. Diimines were reduced selectively to their amino derivatives, and reacted with terephthaldehyde to obtain of a novel symmetrical hexaimines (H-1 and H-2). Their structures were identified on the basis of microanalyses, IR, H-1/C-13 NMR, HRMS and UV-vis spectroscopy. The enol-keto tautomeric equilibrium in these Schiff bases were elucidated by chromically and fluorescence spectra with respect to the influence of solvent, acid-base and light. They acted non-emissive in the solid state (lambda(exc) = 365 nm). Diimines displayed a weak green, bluish-green/blue emission in basic DMSO and DMF solution (v/v, 1:1), but they were non-fluorescent in other media. In contrast to this, hexaimines emitted a strong greenish-blue fluorescence in pure, bluish-green/greenish-blue fluorescence in acidic, and purplish-blue/blue fluorescence in basic aqueous DMSO and DMF media. Mass spectrum of Schiff bases exhibited the ion peaks as following positions: (D-1): m/z (RI%) = 447.1329 (100 %), 424.1517 (60 %), 322.1454 (20 %), 288.0988 (30 %), 102.1277 (55 %) (Fig. S7). (D-2): m/z (RI%) = 422.1361 (20 %), 288.0996 (100 %) (Fig. 6). (H-1): m/z (RI%) = 883.4259 (10 %), 528.2244 (100 %), 510.2038 (20 %), 392.1605 (10 %), 102.1276 (10 %) (Fig. S8). (H-2): m/z (RI%) = 882.3320 (10 %) [M + 2H](+), 434.1278 (40 %), 392.1710 (50 %), 374.1588 (100 %), 322.1523 (10 %), 256.1142 (15 %), 102.1297 (15 %) (Fig. S9). Mass spectral pattern of D-1 displayed [M + 3H](+) ion peak at m/z 424.1517. The base peak was observed at m/z 447.1329, which may be due to [M + 3H+Na](+) ion. And the following fragment ion appeared at m/z 288.0988, which may be due to [C14H14N3O4](+) ion (4-((2-hydroxy-3-methoxybenzylidene)amino)-3-nitrobenzenaminium)). D-2 showed [M + H](+) molecular ion at m/z 422.1361. The similar fragmentation was observed at m/z 288.0996. This base peak may be due to fragment [C14H14N3O4](+) ion (2-((2-hydroxy-3-methoxybenzylidene)amino)-4-nitrobenzenaminium)). H-1 exhibited [M + 3H](+) molecular ion at m/z 883.4259. The base peak was observed at m/z 528.2244, which may be due to [C35H24N6](+) ion (3,3 '-(((2-((4-(((2-amino-5-(methyleneamino)phenyl)imino)methyl) benzylidene)amino)-1,4-phenylene) bis(azanylylidene))bis(methanylylidene)) bis(benzene-1,2-diylium)). In the case of H-2, [M + 2H](+) ion peak was seen at m/z 882.3320. The following fragmentation was observed at m/z 434.1278, which may be belonged to fragment [C30H18N4](+) ion (3,3 '-(((4-((4-((vinylimino)methyl)benzylidene)amino) 1,2phenylene) bis(azanylylidene))bis(methanylylidene)) bis(benzene-1,2-diylium)). The base peak was recorded at m/z 374.1588, which may be due to fragment [C26H208N3](+) ion (3,3 '-(((4-((2-vinylbut-2-en-1-ylidene)amino)-1,2-phenylene)bis(azanylylidene))bis(methanylylidene)) bis(benzene-1-ylium)).