Triazines, Tetrazines, and Fused Ring Polyaza Systems

The review covers work published in the calendar year 2011. Novel reaction chemistry and new ring synthetic methods for 1,2,3-triazines, 1,2,4-triazines, 1,3,5-triazines, tetrazines, and purines are reviewed. © 2012 Elsevier Ltd

Design of ICT-PET fluorescent probes for zinc(II) based on 5-aryl-2,2 '-bipyridines

Rational design of selective and sensitive 'off-on' fluorescent probes for Zn(II) cations exploiting both PET and ICT mechanisms of sensing is illustrated by the synthesis and application of 5-aryl-2,20-bipyridines modified with a dipicolylaminomethyl fragment. The aryl substituent provides tuning of the properties. © 2012 Elsevier Ltd. All rights reserved

The use of the 1,2,4-triazine method of pyridine ligand synthesis for the preparation of a luminescent Pt(II) labeling agent

The 'triazine' methodology for the synthesis of functionalized pyridine ligands proved to be a convenient method for the preparation of a luminescent Pt(II) complex. The key ligand can be assembled easily starting from readily accessible reagents. Further cycloplatination and post-functionalization led to the ready-to-go luminescent 'tag' 2 for peptide labeling. © 2012 Elsevier Ltd. All rights reserved

Modulation of Intersystem Crossing Rate by Minor Ligand Modifications in Cyclometalated Platinum(II) Complexes

Photophysical properties of four new platinum(II) complexes comprising extended ppy (Hppy = 2-phenylpyridine) and thpy (Hthpy = 2-(2'-thienyl)pyridine) cyclometalated ligands and acetylacetonate (acac) are reported. Substitution of the benzene ring of Pt-ppy complexes 1 and 2 with a more electron-rich thiophene of Pt-thpy complexes 3 and 4 leads to narrowing of the HOMO-LUMO gap and thus to a red shift of the lowest energy absorption band and phosphorescence band, as expected for low-energy excited states of the intraligand/metal-to-ligand charge transfer character. However, in addition to these conventional spectral shifts, another, at first unexpected, substitution effect occurs. Pt-thpy complexes 3 and 4 are dual emissive showing fluorescence about 6000 cm(-1) (similar to 0.7S eV) higher in energy relative to the phosphorescence band, while for Pt-ppy complexes 1 and 2 only phosphorescence is observed. For dual-emissive complexes 3 and 4, ISC rates k(ISC) are estimated to be in order of 10(9)-10(10) s(-1)) while k(ISC) of Pt-ppy complexes 1 and 2 is much faster amounting to 10(12) s(-1) or more. The relative intensities of the fluorescence and phosphorescence signals' of Pt-thpy complexes 3 and 4 depend on the excitation wavelength; Showing that hyper-intersystem crossing (HISC) in the complexes is observably significant

Consecutive nucleophilic substitution and aza Diels–Alder reaction—an efficient strategy to functionalized 2,2′-bipyridines

An efficient strategy for the synthesis of functionalized 2,2′-bipyridines is reported. The strategy is based on readily available 3-pyridyl-1,2,4-triazine 4-oxides and uses a reaction sequence of nucleophilic substitution of hydrogen and aza Diels–Alder reaction

Tuning the Excimer Emission of Amphiphilic Platinum(II) Complexes Mediated by Phospholipid Vesicles

Two new amphiphilic platinum­(II) complexes, [Pt­(2-(4-fluorophenyl)-5-(4-dodecyloxyphenyl)­pyridine) (acac)] (<b>Pt-1</b>) and [Pt­(2-(4-dodecyloxyphenyl)-5-(thien-2-yl)-<i>c</i>-cyclopentenepyridine) (acac)] (<b>Pt-2</b>), where acac is acetylacetonate, were synthesized and characterized. Apart from conventional phosphorescence of single molecules (MEmonomer emission), complexes <b>Pt-1</b> and <b>Pt-2</b> also exhibit excimer emission (EE) when embedded into phospholipid vesicles, that is assigned to emissive Pt–Pt excimers. The EE intensity in vesicular media appeared to depend on the viscosity of the vesicles and the concentration of the embedded complex. Differences in the EE properties of complexes <b>Pt-1</b> and <b>Pt-2</b> are correlated with the energies of the π-character frontier orbitals defined by the design of the cyclometalating phenylpyridine ligand. Higher energies of the frontier π-orbitals (HOMO and LUMO) naturally promote stronger π–π interactions, thus obstructing the Pt^II–Pt^II interaction