A comment upon the aggregation of squaraine dyes

被引:20
作者
Ashwell, GJ [1 ]
机构
[1] Cranfield Univ, Ctr Mol Elect, Cranfield MK43 0AL, Beds, England
关键词
D O I
10.1039/a705466a
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The electrospray ionisation mass spectrum (ESI-MS) of 2,4-bis[4-(N-methyl-N-butylamino)phenyl]squaraine shows peaks which correspond to the fragmentation pattern of the dimeric aggregate (e.g. m/z=810 [2M + 2H](+)) and, although the molecule is centrosymmetric, solid solutions of the dye exhibit second-harmonic generation (SHG). In order to satisfy the structural requirement the nonlinear optical behaviour is attributed to the dimeric aggregate which must be non-centrosymmetric. In contrast, solid solutions of the tetrahydroxy analogue, 2,4-bis [4-(N-methyl-N-butylamino)-2,6-dihydroxyphenyl]squaraine, are SHG-inactive and the ESI-MS data are consistent with the formation of a heptameric aggregate (m/z=819 [1.75M](+)=[7M](4+)). The aggregation number is compound specific and an extensive study of fourteen anilino squaraines has shown direct correlation between the type of aggregate and the occurrence or absence of SHG.
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收藏
页码:373 / 376
页数:4
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