Starburst molecule

Y. Kuwabara, H. Ogawa, H. Inada, N. Noma, and Y. Shirota, Thermally stable multilayered organic electroluminescent devices using novel starburst molecules, 4,4, 4"-tri(A-carbazolyl)... 

A very productive strategy for the synthesis of glass-forming materials is the use of highly branched rigid structures. As a suitable center for starburst molecules with a threefold symmetry, triarylamine or benzene are used most frequently. Due to the large number of starburst molecules described in the literature, we divide this class into two subgroups, compounds based on the triarylamine and the benzene centers. 

The Tg can be raised even further if additional phenyl rings are inserted into the branches of these compounds (Fig. 3.12). Based on this concept, starburst molecules with 1,3,5-triphenylbenzene (32) and 1,3,5-triethinylbenzene cores have been reported [77-79]. The Tg of 32 compared with 31 is increased by 23°C. 

Lescanec RL, MuthukumarM. Configurational characteristics and scaling behavior of starburst molecules a computational study. Macromolecules 1990 23 2280-2288. 

Molecular Recognition and Chemistry in Restricted Reaction Spaces. Photophysics and Photoinduced Electron Transfer on the Surfaces of Micelles, Dendrimers and DNA [N. J. Turro, J. K. Barton, D. A. Tomalia, Acc. Chem. Res. 1991, 24, 332], Self-Assembly in Synthetic Routes to Molecular Devices. Biological Principles and Chemical Perspectives A Review [J. S. Lindsey, New J. Chem. 1991,15, 153], Amorphous molecular materials synthesis and properties of a novel starburst molecule, 4,4, 4 -tri(N-phenothiazinyl)triphenylamine [A. Higuchi, H. Inada, T. Kobata, Y. Shirota, Adv. Mat. (Weinheim, Ger.) 1991, 3(11), 549-550],... 

The major efforts to increase Tg include two noteworthy innovative approaches (i) Synthesis of starburst molecules, suitable for HTLs, whose patently nonplanar structure inhibits recrystallization,71 and (ii) synthesis of novel molecules in which familiar luminescent molecules are synthesized around a spiro-bifluorene core.70 As shown by Spreitzer et al.,70 Tg of these spiro derivatives, such as spiro-DPVBi, is considerably higher than that of the parent molecules, yet their PL and EL spectra are essentially identical. As expected, the lifetime of the OLEDs fabricated from the spiro derivatives is considerably higher than that of the parent-compound-based devices, both at room and at elevated temperatures. 

Dendrimeric molecules, also known as cascade molecules or Starburst molecules, represent an architectural class of macromolecules different from both ordinary polymers of the linear or cross-linked classes and biopolymers of the carbohydrate or peptide classes. 

K Imai, (1994). Multilayered organic electroluminescent device using a novel starburst molecule, 4,4, 4 -tiis(3-methylphenylphenylamino)triphenylamine, as a hole transport mateiiaL Appl. Phys. Lett., VoL 65, No. 7, pp. 807-809. 

The reader should also examine References [44-51] for more examples of starburst molecules. The additional references cited therein are also valuable. 

H. Kajii, K. Takahashi, Y. Hino, and Y. Ohmori, Organic light emitting diode using starburst molecule doped with rubrene fabricated by wet-processing for application on an electro-optical conversion device, lEICE Trans. Electron., E87-C(12), 2059-2063 (2004). 

Dendrimers (sometimes called arbor, cascade, or starburst molecules) share some characteristics with polymers but also manifest critical differences. Whereas linear polymers like polystyrene are polydisperse (have a range of molecular weights and character), dendrimers, synthesized in a stepwise manner, are monodisperse (have uniform molecular mass). Unlike polymers, their growth becomes at some stage self-limiting as the molecule folds into itself. Unlike linear polymers, which present countless rapidly interconverting shapes, dendrimers are nearly spherical in shape with diameters typically between 2 and 10 nm. 

Fluorescent chemosensors for the detection of heavy metal ions by a simple fluorescence tum-on (off-on) or quenching (on-ofi) are a fundamental tool for a rapid and nondestructive analysis of biochemical and environmental matrices (2007CSR993). A hot topic is the des p of selective sensors for Hg, one of the most hazardous pollutants of the environment. In this context, a new tren-based starburst molecule containing fluorinated 1,2,4-oxadiazoles as fluorophores has been synthesized and its sensing behavior towards several metal cations has been investigated by UV/Vis, fluorescence. 

Lescanec, R. L. Muthukumar, M. Configurational Characteristics and Scaling Behavior of Starburst Molecules A Computational Study. Macromolecules, 23,2280-2288 (1990). Le, TuC.,Todd,B. D.,Daivis,P. J.,andUhlherr,A. Structural properties of hyperbranched polymers in the melt under shear via nonequUibrium molecular dynamics simulation. The Journal of Chemical Physics 130,074901 (2009). 

Polyamidoamine (PAMAM) systems are perhaps the most studied in the area of electrochemistry in the presence of dendrimers. The uptake of by coordination to amine sites followed by reduction to Cu yielded clusters that have potential use for catalysis [38]. The stabiUty of the small clusters suggested that they reside in the cavities of these starburst molecules. Because PAMAM is a nonspecific ligand, the use of this method of preparing clusters is applicable to a wide range of metals. Moreover, the geometry of dendrimers and the variation of size that is available by controlling the generation number allow the prediction that they can be immobilized by a variety of methods at electrode surfaces. 

Beginning with the work of Thomalia [17] in 1986, starburst molecules (dendrimers) have achieved enormous interest within the last years. Dendrimers are highly branched regular molecules, which are usually prepared by stepwise reactions. In many cases the behaviour of dendritic macromolecules are different from that of linear polymers, e. g. the former... 

For the preparation of the novel starburst molecules, different core molecules have been used 1,3,5-benzene tricarboxylic acid chloride, l,3,5-tris(4-benzoyl)benzene, 1,3,5-triethynylbenzene, and 4,4, 4"trihydroxytriphenylamine. 

The thermal behaviour of the starburst molecules has been investigated by differential scanning calorimetry and thermogravimetric measurements. 

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