Quinacridone Derivatives Research Articles

Supramolecular Structures and Assembly and Luminescent Properties of Quinacridone Derivatives

The synthesis and single-crystal X-ray structures of two quinacridone derivatives, N,N'-di(n-butyl)quinacridone (1) and N,N'-di(n-butyl)-1,3,8,10-tetramethylquinacridone (2), are reported, and the 1H NMR, absorption, photoluminescent (PL), and electroluminescent (EL) characteristics are presented. Both these crystal structures are characterized by intermolecular pi...pi and hydrogen bonding interactions. The intermolecular pi...pi interactions lead to the formation of molecular columns in the solids of 1 and 2, and the interplanar contact distances between two adjacent molecules are 3.48 and 3.55 angstroms, respectively. Crystals of 1 display shorter intermolecular pi...pi contacts and higher density than 2. These results suggest that tighter intermolecular interactions exist in 1. The 1H NMR, absorption, and PL spectra of 1 and 2 in solutions exhibit concentration-dependent properties. The PL quantum yields of 1 in solutions decrease more quickly with the increase of concentration compared to that of 2 in solutions. For solid thin films of Alq3:1 (Alq3 = tris(8-hydroxyquinolinato)aluminum), emission intensities dramatically decrease and obvious red shifts are observed when the dopant concentration is above 4.2%, while for films of Alq3:2, a similar phenomenon occurs when the concentration is above 6.7%. EL devices with Alq3:1 as emitting layer only show high efficiencies (20.3-14.5 cd/A) within the narrow dopant concentration range of 0.5-1.0%. In contrast, high efficiencies (21.5-12.0 cd/A) are achieved for a wider dopant concentration range of 0.5-5.0% when Alq3:2 films are employed as emitting layer. The different PL and EL concentration-dependent properties of the solid thin films Alq3:1 and Alq3:2 are attributed to their different molecular packing characteristics in the solid state.

Two-Dimensional Supramolecular Assemblies of Quinacridone Derivatives: From Achiral to Chiral Racemates and Domains

We described the two-dimensional (2D) assemblies of N,N‘-dialkyl-substituted quinacridone derivatives on highly orientated pyrolytic graphite (HOPG) observed by scanning tunneling microscopy (STM), and focused on how minor structural variations can influence the supramolecular organization of the compounds. For quinacridone derivatives with or without methyl groups only the same enantiotopic faces of the quinacridone cores are observed with high resolution depending on the length of the substituted alkyl chains. For coadsorptions of quinacridone derivatives and fatty acids at the liquid/graphite interface, we have found interestingly that quinacridone derivatives with methyl groups form chiral racemates, whereas the quinacridone derivative without methyl groups forms chiral domains. The chiral 2D structures formed at the interface are only observed when fatty acids are present as guest molecules and for quinacridone derivatives substituted with long alkyl chains, −C22H45. These findings suggest that the 2D nanopatterned structure of quinacridone derivatives with light-emitting properties can be adjusted by controlling intermolecular interaction through tailor-made molecular building blocks and coadsorption.

In Situ Scanning Tunneling Microscopic Investigation of the Two-Dimensional Ordering of Different Alkyl Chain-Substituted Quinacridone Derivatives at Highly Oriented Pyrolytic Graphite/Solution Interface

Adlayers of N-alkyl-substituted quinacridone derivatives have been imaged at highly oriented pyrolytic graphite (HOPG)/solution interfaces by scanning tunneling microscopy (STM). The quinacridone derivatives bearing long alkyl chains form stripe patterns, which are attributed to the physisorption induced by the HOPG surface. The well-resolved alkyl chains suggest relatively high stability and ideal packing of the long chains on the graphite surface. For derivatives bearing short alkyl chains, a grainlike structure is formed, but alkyl chains are not resolved. When quinacridone derivatives bearing long and short alkyl chains are mixed, a hexagon honeycomb structure is observed as a transition state. However, this transition state is not stable and it separates out spontaneously to form the two above-mentioned stable domain structures for long and short alkyl chains.

Color Generation Mechanism of Quinacridone Derivatives as Viewed from the Intermolecular Hydrogen Bond

Quinacridones are industrially important hydrogen-bonded pigments. The shade in the solid state is vivid red while pale yellow in solution, indicating the involvement of intermolecular interactions in the color generation. The electronic structure has therefore been investigated based on the crystal structure with special attention to the intermolecular N–H…O hydrogen bond using four kinds of quinacridone compounds with different H-bond forming characteristics: unsubstituted quinacridone (γ-QA), mono- N-methylquinacridone (MMQA), N,N′-dimethylquinacridone (DMQA) and 2,9-dimethylquinacridone (2,9-DMQA). γ-QA, 2,9-DMQA and MMQA are found to form three-dimensional (“hunter's fence”), two-dimensional (sheet-like) and one-dimensional (chain-like) hydrogen bond networks, respectively. The present H-bond aligns the transition dipole in a way “head-to-tail”. The bathochromic shift upon crystallization (pale yellow to vivid red) is mostly attributed to resonance interactions between transition dipoles.

Aggregation Properties of Soluble Quinacridones in Two and Three Dimensions

The aggregation properties of derivatives of linear trans-quinacridone, an archetypal pigment, have been explored in two and three dimensions. The sparse solubility of the parent quinacridone pigment in common organic solvents can be traced back to the formation of a network of hydrogen bonds. Introducing aliphatic substituents on specific positions of the quinacridone core leads to an increased solubility without hampering the formation of intermolecular hydrogen bonds. With UV−Vis absorption, steady-state fluorescence, and infrared spectroscopy, the aggregation behavior of these substituted quinacridone derivatives is studied. On the basis of these data, models are proposed for the aggregate structure in solution. In addition, the two-dimensional ordering on graphite of these compounds and N,N‘-dialkylated analogues has been investigated with scanning tunneling microscopy. The comparison between the two-dimensional organization and the solution data allows one to identify the extent of intermolecular in...

Effect of Hydrogen-bonding on Crystal Structure of Quinacridone Derivatives in Thin Film

The different crystal behaviors are found in two quinacridone compounds (QD and QD-Me) films grown epitaxially on an air-cleaved KBr (001) substrate. It is considered to imply the substitution effect on the hydrogen-bonding formation according to the investigation of both absorption properties and crystal structure.

Characterization of Quinacridone Derivative in Thin Film

2,9-Dimethyl quinacridone (QD-Me) grew epitaxially on a KBr substrate took two kinds of molecular orientations. The absorption property of QD-Me film depended on the molecular orientation. When QD-Me molecules oriented parallel to the substrate surface, the intermolecular charge transfer was contributed effectively to the absorption intensity in the short wavelength region.

Orientation Control of Quinacridone Derivatives with Long Alkyl Chains in Langmuir-Blodgett Films

Abstract By introducing four alkyl chains to quinacridone, the soluble derivatives can be spread as monolayers on water surface and their surface pressure – area isotherms were found to depend significantly on the temperature and the alkyl chain length. Different orientations and packings were realized, depending on the alkyl substituents.

キナクリドン誘導体の合成

キナクリドン誘導体の合成