Luminescent metallogels of platinum(II) terpyridyl complexes: interplay of metal...metal, pi-pi and hydrophobic-hydrophobic interactions on gel formation

A series of platinum(II) terpyridyl complexes has been demonstrated to show gelation properties driven by Pt...Pt and pi-pi interactions in addition to hydrophobic-hydrophobic interactions; counter-anions have been found to affect strongly the colour of the metallogel.     

A class of luminescent cyclometalated alkynylgold(III) complexes: synthesis, characterization, and electrochemical, photophysical, and computational studies of [Au(C=N=C)(C triple bond C-R)] (C=N=C = kappa(3)C,N,C bis-cyclometalated 2,6-diphenylpyridyl)

A new class of luminescent cyclometalated alkynylgold(III) complexes, [Au(RC=N(R')=CR)(CCR' ')], i.e., [Au(C=N=C)(C triple bond CR')] (HC=N=CH = 2,6-diphenylpyridine) R' ' = C6H5 1, C6H4-Cl-p 2, C6H4-NO2-p 3, C6H4-OCH3-p 4, C6H4-NH2-p 5, C6H4-C6H13-p 6, C6H13 7, [Au(tBuC=N=CtBu)(C triple bond CC6H5)] 8 (HtBuC=N=CtBuH = 2,6-bis(4-tert-butylphenyl)pyridine), and [Au(C=NTol=C)(CCC6H4-C6H13-p)] 9 (HC=NTol=CH = 2,6-diphenyl-4-p-tolylpyridine), have been synthesized and characterized. The X-ray crystal structures of most of the complexes have also been determined. Electrochemical studies show that, in general, the first oxidation wave is an alkynyl ligand-centered oxidation, while the first reduction couple is ascribed to a ligand-centered reduction of the cyclometalated ligand with the exception of 3 in which the first reduction couple is assigned as an alkynyl ligand-centered reduction. Their electronic absorption and luminescence behaviors have also been investigated. In dichloromethane solution at room temperature, the low-energy absorption bands are assigned as the pi-pi* intraligand (IL) transition of the cyclometalated RC=N(R')=CR ligand with some mixing of a [pi(C triple bond CR') --> pi*(RC=N(R')=CR)] ligand-to-ligand charge transfer (LLCT) character. The low-energy emission bands of all the complexes, with the exception of 5, are ascribed to origins mainly derived from the pi-pi* IL transition of the cyclometalated RC=N(R')=CR ligand. In the case of 5 that contains an electron-rich amino substituent on the alkynyl ligand, the low-energy emission band was found to show an obvious shift to the red. A change in the origin of emission is evident, and the emission of 5 is tentatively ascribed to a [pi(CCC6H4NH2) --> pi*(C=N=C)] LLCT excited-state origin. DFT and TDDFT computational studies have been performed to verify and elucidate the results of the electrochemical and photophysical studies.     

Functionalized BODIPY with various sensory units - a versatile colorimetric and luminescent probe for pH and ions

A series of BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) derivatives containing ion- and pH-sensory units have been successfully designed and synthesized. One of the compounds was structurally characterized by X-ray crystallography. Owing to the presence of an ICT absorption band, one of the compounds was found to show pronounced solvatochromic behavior in different organic solvents. Their emission energies in various solvents show a linear dependence on the Lippert solvent parameter. The cation-binding properties of the complexes with different metal ions (alkali metal, alkaline earth metal and transition metal ions) have been studied using UV-vis and emission spectroscopies. A 1?:?1 complexation to metal ions (Li(+), Na(+), Mg(2+), Ba(2+), Zn(2+), Cd(2+)) was found for the compound with one azacrown moiety in acetonitrile while another one with two azacrown moieties was shown to form 1?:?2 complexes with Zn(2+) and Mg(2+) cations. Their stability constants have been determined by both UV-vis and emission spectrophotometric methods. By introducing triarylborane moieties into the meso position and the 2-position of the BODIPY skeleton, different electronic absorption spectral changes together with an emission diminution were observed in response to fluoride ions. Ditopic binding study of 5, which was functionalized with both azacrown and triarylborane moieties, showed emission enhancement in the presence of Mg(2+) and F(-). These findings suggest that these BODIPY derivatives are capable of serving as versatile colorimetric and luminescence probes for pH, cations and F(-).