The synthesis of singlet ground state derivatives of non-Kekulé polynuclear aromatics
作者:Graeme Allinson、Richard J. Bushby、Malini V. Jesudason、Jean-Louis Paillaud、Norman Taylor
DOI:10.1039/a606932k
日期:——
It is known that a two-electron reduction of tetrabutylammonium
3,4-dioxo-4H,8H-dibenzo[cd,mn]pyren-
12-olate gives a trioxy (tri-O-) derivative of the
non-Kekulé polynuclear aromatic compound
dibenzo[cd,mn]pyrene (triangulene). This derivative is
stable in solution and, like triangulene itself, has a triplet ground
state. In exploring the generality of this strategy for the synthesis of
high-spin derivatives of non-Kekulé polynuclear aromatic compounds
we have investigated two electron reductions of
4,8-dioxo-4H,8H-dibenzo[cd,mn]pyrene
(to give a dioxy derivative of triangulene),
7,8-dioxo-7H,8H-dibenzo[de,hi
]naphthacene (to give a dioxy derivative of
dibenzo[de,hi]naphthacene) and
7,9-dioxo-7H,9H-dibenzo[de,jk
]pentacene (to give a dioxy derivative of
dibenzo[de,jk]pentacene).
Dibenzo[cd,mn]pyrene (triangulene),
dibenzo[de,hi]naphthacene and
dibenzo[de,jk]pentacene should all have triplet
ground states, but the presence of two O-
substituents on these aromatic nuclei will (just) lift the
degeneracy of the putative singly occupied molecular orbitals. We have
shown that the splitting this produces is sufficient to ensure that all of
these dioxy derivatives have singlet ground states. Hence the strategy
employed for making and stabilising triplet triangulene as its trioxy
derivative does not provide a paradigm for other high-spin
non-Kekulé polynuclear aromatics. The reduction reactions were
studied by cyclic voltammetry, by UV–VIS spectroscopy, and by EPR
spectroscopy. Improved synthetic routes are described for
7,8-dioxo-7H,8H-dibenzo[de,hi
]naphthacene and for
7,9-dioxo-7H,9H-dibenzo[de,jk
]pentacene. Violent explosions were encountered in attempts to repeat
the literature procedure for the synthesis of
4,6-dichlorobenzene-1,3-dicarboxylic acid.
已知,四丁基铵3,4-二氧-4H,8H-二苯并[cd,mn]芘-12-olate的二电子还原反应产生非Kekulé多核芳香化合物二苯并[cd,mn]芘(三角烯)的三氧(tri-O-)衍生物。这种衍生物在溶液中稳定,并且像三角烯本身一样,具有三重态基态。在探索这种策略合成非Kekulé多核芳香化合物的高自旋衍生物的普遍性时,我们研究了4,8-二氧-4H,8H-二苯并[cd,mn]芘(产生三角烯的二氧衍生物)、7,8-二氧-7H,8H-二苯并[de,hi]萘并萘(产生二苯并[de,hi]萘并萘的二氧衍生物)和7,9-二氧-7H,9H-二苯并[de,jk]戊搭烯(产生二苯并[de,jk]戊搭烯的二氧衍生物)的二电子还原反应。二苯并[cd,mn]芘(三角烯)、二苯并[de,hi]萘并萘和二苯并[de,jk]戊搭烯都应该具有三重态基态,但这些芳香核上有两个O取代基的存在(恰好)会解除假定的单占据分子轨道的简并性。我们已经证明,这种分裂产生的分裂足以确保所有这些二氧衍生物具有单重态基态。因此,用于制造和稳定三重态三角烯作为其三氧衍生物的策略并不为其他高自旋的非Kekulé多核芳香化合物提供范例。还原反应通过循环伏安法、紫外-可见光谱和电子顺磁共振光谱进行了研究。还描述了7,8-二氧-7H,8H-二苯并[de,hi]萘并萘和7,9-二氧-7H,9H-二苯并[de,jk]戊搭烯的改进合成路线。在尝试重复文献中4,6-二氯苯-1,3-二羧酸的合成步骤时,遭遇了剧烈的爆炸。