Design, Synthesis, Characterization, and OFET Properties of Amphiphilic Heteroleptic Tris(phthalocyaninato) Europium(III) Complexes. The Effect of Crown Ether Hydrophilic Substituents

Two amphiphilic heteroleptic tris(phthalocyaninato) europium complexes with hydrophilic crown ether heads and hydrophobic octyloxy tails [Pc(mCn)(4)]Eu[Pc(mCn)(4)]Eu[Pc(OC8H17)(8)] [m = 12, n = 4, H2Pc(12C4)(4) = 2,3,9,10,16,17,23,24-tetrakis(12-crown-4)phthalocyanine; m = 18, n = 6, H2Pc(18C6)(4) = 2,3,9,10,16,17,23,24-tetrakis(18-crown-6)phthalocyanine; H2Pc(OC8H17)(8) = 2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyanine] (1, 2) were designed and prepared from the reaction between homoleptic bis(phthalocyaninato) europium compound [Pc(mCn)(4)]Eu[Pc(mCn)(4)] (m = 12, n = 4; m = 18, n = 6) and metal-free H2Pc(OC8H17)(8) in the presence of Eu(acac)(3) center dot H2O (Hacac = acetylacetone) in boiling 1, 2,4-trichlorobenzene. These novel sandwich triple-decker complexes were characterized by a wide range of spectroscopic methods and electrochemically studied. With the help of the Langmuir-Blodgett technique, these typical amphiphilic triple-decker complexes were fabricated into organic field effect transistors (OFET) with top contact configuration on bare SiO2/Si substrate, hexamethyldisilazane-treated SiO2/Si substrate, and octadecyltrichlorosilane (OTS)-treated SiO2/Si substrate, respectively. The device performance is revealed to be dependent on the species of crown ether substituents and substrate surface treatment. OFETs fabricated from the triple decker with 12-crown-4 hydrophilic substituents, 1, allow the hole transfer in the direction parallel to the aromatic phthalocyanine rings. In contrast, the devices of a triple-decker compound containing 18-crown-6 as hydrophilic heads, 2, transfer holes in a direction along the long axis of the assembly composed of face-to-face aggregated triple-decker molecules, revealing the effect of molecular structure, specifically the crown ether substituents on the film structure and OFET functional properties. The carrier mobility for hole as high as 0.33 cm(2) V-1 s(-1) and current modulation of 7.91 x 10(5) were reached for the devices of triple-decker compound 1 deposited on the OTS-treated SiO2/Si substrates, indicating the effect of substrate surface treatment on the OFET performance due to the improvement on the film quality as demonstrated by the atomic force microscope investigation results.