Quinacridone Research Articles

Excitation Migration from Photoexcited Tris(8-hydroxyquinolino)aluminium to Quinacridone in Codeposited Thin Films

Absorption, fluorescence, and time-resolved fluorescence measurements have been carried out to demonstrate the energy transfer from photoexcited tris(8-hydroxyquinolino)aluminium (ALQ) to quinacridone (QA) in codeposited thin films. All the results indicate that the excitation energy is transferred from ALQ to QA, which distribute randomly in three dimensions in the thin films, by the Förster mechanism. From the analyses of the fluorescence decay of ALQ, the critical distance for the energy transfer between ALQ and QA molecules is determined to be 26 Å. This value is in good agreement with that calculated from the fluorescence spectra of ALQ, the absorption spectra of QA, and the fluorescence quantum efficiency of ALQ. This agreement also indicates that energy migration among ALQ molecules is not an efficient process.

Spectral properties of organic chromophores in fluorophosphate glasses

Rhodamine 6G, Alq 3, quinacridone (QAD) doped lead tin fluorophosphate glass samples (62.3SnF 2, 10.8SnO, 9.5PbF 2, 17.4P 2O 5 wt%) were prepared. Glass samples were melted at 320°C in an electric furnace in a pyrex crucible, then were transferred to a Teflon crucible in another furnace at 280°C. The glass transition temperature, crystallization temperature, melting temperature, refractive index, and chemical durability in water were measured. The absorption spectra and emission spectra of organic chromophores in these samples were measured. The absorption peak shifts from 537.2 (±0.2) to 535.8 (±0.2) nm and the emission peak shifts from 585.0 (±0.5) to 589.0 (±0.5) when the melting time of Rhodamine 6G increased from 15 to 60 min. The energy transfer from Alq 3 to QAD and Rhodamine 6G were investigated by excitation spectra analysis. The results showed that the energy absorbed by Alq 3 from 350 to 450 nm was transferred to QAD, which is important for active devices.

Electronic spectra of 7,14‐dithioketo‐5,7,12,14‐tetrahydroquinolino‐[2,3‐b]‐acridine in solution and in the solid state

Abstract7,14‐Dithioketo‐5,7,12,14‐tetrahydroquinolino‐[2,3‐b]‐acridine (DTQ) is a thionated derivative of quinacridone (QA) that is known as a red pigment. Thionation of QA brings about an intense near‐IR absorption in the solid state which is of practical importance for GaAsAl‐laser printers and optical information storage systems. The electronic properties of DTQ have been investigated in solution and in the solid state in order to characterize the near‐IR absorption from the standpoint of intermolecular hydrogen bonding. The electronic state of the DTQ‐chromophore is found to be most sensitively affected by an environment of proton acceptors which interact with the NH group of the chromophore. In solution, the hydrogen bonds between the NH group and the O atom of a solvent cause a bathochromic shift by 5 – 15 nm relative to the absorption spectrum in dioxane. This is interpreted as being due to electron transfer from the proton to the nitrogen atom, thereby increasing the electron density in the chromophore. A similar increase in electron density is also operative in the solid state through the intermolecular hydrogen bonds between the NH group of one DTQ and the S atom of the neighboring molecule. This is mainly responsible for the bathochromic displacement of DTQ in going from solution to the solid state. The near‐IR absorption is, however, not explicable in terms of the hydrogen bonding interaction alone. Another intermolecular interaction, such as π‐π interactions along the stacking axis, appears to be operative that might lead to a near‐IR absorption.

Recent Survey of Quinacridones and Related Compounds.

Recent Survey of Quinacridones and Related Compounds.