Microwave-assisted one-pot synthesis of new ionic iridium complexes of [Ir(bzq)2(N

Iridium C,N-cyclometalated complexes with an ionic structure are considered to be promising candidates for application in host/guest solid-state phosphorescent single-layer devices because the employment of such dopants offers the possibility of reducing their concentration in organic matrices as well as allows obtaining organic light emitting devices (OLEDs) with interesting emission parameters. We report herein a methodology enabling the synthesis of cyclometalated ionic iridium(iii) complexes of the type [Ir(C^N)2(N^N)]+A- according to a three-component one-pot strategy involving the acceleration of the reaction via microwave irradiation. The developed protocol allowed efficient synthesis of a series of new cationic iridium(iii) coordination derivatives, which were isolated and spectroscopically characterized, while the structures of two of them were determined by the X-ray method. Moreover, the iridium(iii) derivatives were subjected to the cyclic voltammetry studies in order to determine the energies of the HOMO and LUMO levels as well as to estimate their electrochemical properties and to predict some electronic properties. Additionally, the ONIOM calculation scheme that was used to predict HOMO-LUMO gaps for the studied Ir(iii) complexes showed a good correlation between the experimental and calculated values. In order to determine the influence of the structure and nature of the ancillary ligand on the location of the maximum emission band, the photophysical properties of the synthesized iridium complexes were characterized. Finally, the selected compounds were used as emitters for the construction of polymer light emitting diodes (PLEDs) based on a poly(N-vinylcarbazole)/2-(4-tert-butylphenyl)-5-(4-biphenyl)-1,3,4-oxadiazole (PVK/PBD) matrix. The highest luminance, above 10 000 cd m-2, was recorded for the device containing only 1.0 wt% of [Ir(bzq)2(1,10-phenanthroline)]+PF6- in the PVK/PBD. The fabricated PLEDs exhibit current efficiency in the range of 1.0 to 2.2 cd A-1.

UV-vis absorption spectra of 1,4-dialkoxy-2,5-bis[2-(thien-2-yl)ethenyl]benzenes.

Complex theoretical and experimental studies and quantum-chemical calculations were applied to study the UV-vis spectroscopic features of the novel compounds: three stereoisomers of 1,4-diethoxy-2,5-bis[2-(5-methylthien-2-yl)ethenyl]benzene (A-C) and E,E isomer of 1,4-diisopropoxy-2,5-bis[2-(thien-2-yl)ethenyl]benzene (D). These structures are the derivatives of 2,5-bis[2-(thien-2-yl)ethenyl]benzene, and belong to a group of thienyl-PPV family that are able to polymerize due to the presence of pi-conjugated bonding system. It was established that such compounds during electropolymerization are strongly dependent on their stereochemistry and on the eventual presence of substituents in alpha-positions of the tiophene ring. We have obtained a good agreement between the theoretically simulated optical within a framework of TDDFT approach and experimentally measured data. Influence of PMMA polymer matrices on the UV-vis spectra is explored. It is shown that a red wavelength spectral shift is observed only for D compounds and agreement between calculated and experimental spectral data is sufficiently good. This may indicate on different influence of local polymer matrix field on the spectral behaviors of the chromophores with different stereochemistry.

In situ self hardening bioactive composite for bone and dental surgery.

A new biomaterial is presented which consists of a cellulose derivative--silanised hydroxyethylcellulose (HEC-SIL) and biphasic calcium phosphate (BCP). Rheological properties of the polymer itself and its mixture with BCP are pH-dependent. At pH 10-12 HEC-SIL is liquid and undergoes quick gellation at pH < 9. Similarly, the paste of HEC-SIL and BCP is fluid and injectable at higher pH and solidifies in biological solutions. The rate of this solidification can be easily controlled by the degree of substitution of hydroxyethylcellulose with silicoalkoxy groups.

Application of FT-IR microspectroscopy to the study of an injectable composite for bone and dental surgery.

Hydroxypropylmethylcellulose (HPMC) of high-viscosity grade is used as a ligand for a bioactive calcium phosphate ceramic (the filler) in a ready-to-use injectable sterilized biomaterial for bone and dental surgery. Application of physico-chemical methods such as XPS, NMR, or Raman spectroscopy encounters difficulties when used to study such a multiphased material. This paper reports on the application of FT-IR microspectroscopy (FT-IRM) for the investigation of inorganic and organic phases of the rough composite and separated phases obtained by mechanical or chemical extraction methods. A comparison of FT-IRM with the conventional KBr pellet method was made and indicates that the macro and micro FT-IR methods are complementary: the former revealed new chemical groups not visualized with the KBr method whereas the latter detected the major compound of the blend. FT-IR microspectroscopy was revealed to be a powerful method of analysis that is complementary to other existing spectroscopic methods. Moreover, it is expected to be a useful tool in the study of biomaterials in biological samples.

Fourier-transform infrared spectroscopy study of an organic-mineral composite for bone and dental substitute materials.

A new injectable biomaterial for bone and dental surgery is a composite consisting of a polymer as a matrix and bioactive calcium phosphate (CaP) ceramics as fillers. The stability of the polymer is essential in the production of a ready-to-use injectable sterilized biomaterial. The purpose of this study was to detect possible polymer degradation which may have been caused by the interaction with the fillers using Fourier transform infrared spectroscopy. Composites containing CaP fillers (biphasic calcium phosphate, hydroxyapatite and peroxidized hydroxyapatite) and polymer (hydroxypropyl methyl cellulose) were prepared. To investigate the properties of the polymer, the inorganic and organic phases of the composite were separated using several extraction methods. The difficulty in separating the organic (polymer) from the mineral (CaP fillers) phases in the composite investigated in this study suggested the presence of strong interactions between the two phases. Spectra of extracted polymers showed new absorption bands of low intensities and indications that some chemical modifications of the original polymers have occurred. Results also indicated that the filler composition has an effect on the integrity of the polymer.