Neutral phosphorus-containing dendrimers with aldehyde groups at the periphery have been analyzed using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOFMS) up to generation four. Although the expected quasi-molecular ion is generally observed, the mass spectral pattern, presence of fragments and adducts related to the original skeleton, is highly relevant to the sample preparation (nature of the matrix: 2-5-dihydroxybenzoic acid (2.5-DHB), 1,8-dihydroxy-9[10H]-anthracenone (dithranol), 6-azathiothymine, 2,4,6-trihydroxyacetophenon, 7-hydroxycoumarin or 2-anthramine, and addition of alkali metal salts). The dithranol matrix with addition of LiI offers milder conditions; however, abundant fragments are still observed for the higher generation dendrimers. Investigation of these effects in connection with SEC, NMR, and MALDI-TOFMS studies of UV preirradiated dendrimers allows the assumption to be made that fragmentation occurs in MALDI due to the relatively strong absorption of the dendrimers at 337 nm. Fragmentations and formation of adducts involve nitrogen−nitrogen bond cleavage, imine metathesis, and reaction of aldehyde groups with internal imino groups.
使用基质辅助激光解吸电离飞行时间质谱(
MALDI-TO
FMS)对中性含
磷树枝状分子外围的醛基进行了分析,分析结果可追溯到第四代。虽然通常可以观察到预期的准分子离子,但质谱图、碎片和与原始骨架相关的加合物的存在与样品制备(基质的性质:2-5-二羟基
苯甲酸(2.5-DHB)、1,8-二羟基-9[10H]-
蒽酮(二
萘酚)、6-
氮杂
硫代
胸苷、
2,4,6-
三羟基
苯乙酮、7-羟基
香豆素或2-
蒽胺,以及碱
金属盐的添加)高度相关。添加LiI的二
萘酚基质提供了更温和的条件;然而,对于更高代数的树枝状分子,仍然观察到大量碎片。通过结合
SEC、NMR和
MALDI-TO
FMS对紫外线预照射树枝状分子进行研究,可以推测
MALDI中发生碎片化是由于树枝状分子在337 nm处具有相对较强的吸收。碎片化和加合物的形成涉及
氮-
氮键断裂、
亚胺复分解反应以及醛基与内部亚
氨基的反应。