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indeno [3,2-b]thiophene] (spiro-FIT) and bis(spiro-FIT)arenes were synthesized. The UV/ vis spectra, emission spectra, and cyclic voltammetry of these compounds are described.Recently, p-conjugated compounds such as organic lightemitting diodes (OLED), photovoltaic cell, and organic field-effect transistors (OFET) have received considerable attention in the field of organic electronics. In particular, thiophene-based compounds such as poly-and oligothiophenes are among the most studied organic materials because of their charge-transport properties. 1 Thiophene/phenylene 1c,2 and thiophene/fluorene 1c,3 cooligomers have also been widely studied for applications in OFET and OLED. These oligomers show better oxidative stability than the all-thiophene analogues and are stable in air. However, these thiophene-based compounds often face the problem of limited solubility. The incorporation of alkyl chains into the thiophene backbone results in improved solubility. Their photoluminescence efficiencies (F F ) are usually low because of increased nonradiative decay, because the alkylated compounds tend to interact with adjacent molecules in the solid state. 1a The interchain interaction is effective for applications in OFET, but another type of method to increase the solubility of the materials for OLED is needed. 9,9¢-Spirobifluorene derivatives are regarded as the most promising candidates for construction of organic optoelectronics. 4 The rigidity of spiro compounds provides a high glass-transition temperature (T g ) and decomposition temperature (T d ), which are very important for the application of low-molecular-weight compounds to optoelectronic devices. In addition, their solubility is higher than that of the corresponding compounds without a spiro moiety, because their perpendicular conformations based on the spiro linkage efficiently suppress intermolecular interactions between the p-systems. Thus, it is expected that the solubility and F F in the solid state of thiophene-based compounds would be improved by incorporation of a spiro moiety into their framework. However, to the best of our knowledge, there are few reports on spiro compounds containing thiophene rings. 5In this paper, we wish to report the synthesis and properties of the thiophene-containing spiro compounds, spiro[fluorene-9,4¢-[4H]indeno[3,2-b]thiophene] (spiro-FIT) and bis(spiro-FIT)arenes. The optical and electrochemical characteristics of bis(spiro-FIT)arenes are easily tunable by changing the linking arenes. The Stille coupling reaction can be used for their synthesis, and, thus, desirable materials for practical applications to OLED can be obtained.Scheme 1 depicts the synthesis of spiro-FIT and its derivatives. 6a,b The reaction of 9-fluorenone with the Grignard reagent derived from 1-bromo-2-thienylbenzene afforded alcohol 1 in 58% yield. An acid-promoted intramolecular alkylation furnished a thiophene-containing spiro compound spiro-FIT in 96% yield. Bromination of spiro-FIT with NBS or lithiation of spiro-FIT followed by reaction with B...

In this paper we consider when a Kaehler submanifold of a complex space form is Einstein with respect to the induced metric. Then we shall show that (1) a 2-dimensional complete Kaehler submanifold M of a 4-dimensional complex projective space P4(C) is Einstein if and only if M is holomorphically isometric to P2(C) which is totally geodesic in P4(C) or a hyperquadric Q2(C) in P3(C) which is totally geodesic in PA(C), and that (2) if M is a 2-dimensional Einstein Kaehler submanifold of a 4-dimensional complex space form A/4(c) of nonpositive constant holomorphic sectional curvature c, then M is totally geodesic.