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The reaction of Re(CO)5Br with deprotonated 1H‐(5‐(2,2′:6′,2′′‐terpyridine)pyrid‐2‐yl)tetrazole yields a triangular assembly formed by tricarbonyl Re(I) vertices. Photophysical measurements reveal blue‐green emission with a maximum at 520 nm, 32 % quantum yield, and 2430 ns long‐lived excited state decay lifetime in deaerated dichloromethane solution. Coordination of lanthanoid ions to the terpyridine units red‐shifts the emission to 570 nm and also reveals efficient (90 %) and fast sensitisation of both Eu(III) and Yb(III) at room temperature, with a similar rate constant kET on the order of 107 s−1. Efficient sensitisation of Eu(III) from Re(I) is unprecedented, especially when considering the close proximity in energy between the donor and acceptor excited states. On the other hand, comparative measurements at 77 K reveal that energy transfer to Yb(III) is two orders of magnitude slower than that to Eu(III). A two‐step mechanism of sensitisation is therefore proposed, whereby the rate‐determining step is a thermally activated energy transfer step between the Re(I) centre and the terpyridine functionality, followed by rapid energy transfer to the respective Ln(III) excited states. At 77 K, the direct Re(I) to Eu(III) energy transfer seems to proceed via a ligand‐mediated superexchange Dexter‐type mechanism. [ABSTRACT FROM AUTHOR]

A family of three neutral iridium(III) tetrazolato complexes are investigated as bacterial imaging agents. The complexes offer a facile tuning of the emission colour from green (520 nm) to red (600 nm) in aqueous media, while keeping the excitation wavelength unchanged. The three complexes do not inhibit the bacterial growth of Bacillus Cereus, used as a model in this study, and exhibit extremely fast cellular uptake. After a minute incubation time, the nontoxic complexes show subcellular localisation in spherical structures identified as lipid vacuoles. Confocal Raman imaging has been exploited for the first time on live bacteria, to provide direct and label‐free mapping of the lipid‐enriched organelles within B. cereus, complementing the use of luminescent probes. Examination of the Raman spectra not only confirmed the presence of lipophilic inclusions in B. cereus but offered additional information about their chemical composition, suggesting that the lipid vacuoles may contain polyhydroxybutyrate (PHB). [ABSTRACT FROM AUTHOR]

Four new tetrazole-containing species, in conjugation with terpyridine moieties through phenyl or pyridyl linkers, have been synthesised and characterised. In the series, the tetrazole functional groups are either in their acidic form or are alkylated at the N2 position with a methyl group. The photophysical properties of the species reveal moderate UV or efficient blue fluorescent emission, with photoluminescence quantum yields of around 30 % and 80 % for UV and blue emission, respectively. The spectral profiles can be reversibly modulated through protonation/deprotonation, with changes being consistent with an increase of the electron density on the tetrazole rings upon deprotonation or a decrease of the electron density on the terpyridines through protonation. The tetrazole-containing species were also investigated for fluorescence sensing of biologically and environmentally important metal ions, highlighting a ratiometric response to the presence of Zn2+. Furthermore, this ratiometric response could be well discriminated from that of interfering Cd2+ ions. Lastly, the species have been investigated as ligands for Eu3+ and Yb3+ cations, revealing efficient sensitisation, to give typical red and near-infrared emissions, respectively. [ABSTRACT FROM AUTHOR]

A family of five neutral cyclometalated iridium(III) tetrazolato complexes and their methylated cationic analogues have been synthesised and characterised. The complexes are distinguished by variations of the substituents or degree of π conjugation on either the phenylpyridine or tetrazolato ligands. The photophysical properties of these species have been evaluated in organic and aqueous media, revealing predominantly a solvatochromic emission originating from mixed metal-to-ligand and ligand-to-ligand charge transfer excited states of triplet multiplicity. These emissions are characterised by typically long excited-state lifetimes (∼hundreds of ns), and quantum yields around 5-10 % in aqueous media. Methylation of the complexes caused a systematic red-shift of the emission profiles. The behaviour and the effects of the different complexes were then examined in cells. The neutral species localised mostly in the endoplasmic reticulum and lipid droplets, whereas the majority of the cationic complexes localised in the mitochondria. The amount of complexes found within cells does not depend on lipophilicity, which potentially suggests diverse uptake mechanisms. Methylated analogues were found to be more cytotoxic compared to the neutral species, a behaviour that might to be linked to a combination of uptake and intracellular localisation. [ABSTRACT FROM AUTHOR]

The reaction of hydrated lanthanoid chlorides with tribenzoylmethane and an alkali metal hydroxide consistently resulted in the crystallization of neutral tetranuclear assemblies with the general formula [Ln(Ae ⋅HOEt)( L)4]2 (Ln=Eu3+, Er3+, Yb3+; Ae=Na+, K+, Rb+). Analysis of the crystal structures of these species revealed a coordination geometry that varied from a slightly distorted square antiprism to a slightly distorted triangular dodecahedron, with the specific geometrical shape being dependent on the degree of lattice solvation and identity of the alkali metal. The near-infrared (NIR)-emitting assemblies of Yb3+ and Er3+ showed remarkably efficient emission, characterized by significantly longer excited-state lifetimes ( τobs≈37-47 μs for Yb3+ and τobs≈4-6 μs for Er3+) when compared with the broader family of lanthanoid β-diketonate species, even in the case of perfluorination of the ligands. The Eu3+ assemblies show bright red emission and a luminescence performance ( τobs≈0.5 ms, ${{\Phi}{{{\rm L}\hfill \atop {\rm Ln}\hfill}}}$≈35-37 %, ηsens≈68-70 %) more akin to the β-diketonate species. The results highlight that the β-triketonate ligand offers a tunable and facile system for the preparation of efficient NIR emitters without the need for more complicated perfluorination or deuteration synthetic strategies. [ABSTRACT FROM AUTHOR]

Tris(aryltriazolylmethyl)amine compounds have been synthesized by a one-pot triple click reaction of azides from anilines with tripropargylamine. The resulting tripodal ligands have been employed to obtain six new Ce3+ complexes. The formation of the new complexes, which were obtained both as heteroleptic or homoleptic types, is influenced by the nature of the counterion (nitrate, perchlorate, or triflate) of the starting Ce3+ salts. All the new Ce3+-based complexes are highly stable both in solution and in the solid state. Their structural features have been at first studied by NMR spectroscopy. In addition, by combining experimental and DFT theoretical approaches, the X-ray structure of one heteroleptic complex has been used to simulate the structures of all the remaining complexes. Finally, both the heteroleptic and the homoleptic complexes are luminescent, and the analysis of their photophysical properties indicate that the Ce3+ center regulates the occurrence of radiative processes. [ABSTRACT FROM AUTHOR]

A new family of mono- and dinuclear ruthenium polypyridyl complexes containing 5-aryltetrazolate ligands such as the deprotonated form of 4-(1H-tetrazol-5-yl)benzonitrile (4-TBNH) and bis(1H-tetrazol-5-yl)benzene (BTBH2) have been synthesized and thoroughly characterized. The reactivity of the mononuclear species toward different electrophiles such as H+ and CH3+ has been investigated, and the effects of the resulting regioselective electrophilic attacks on the electronic and structural properties of the tetrazolate ligand have been studied by NMR (¹H, 13C) spectroscopy and X-ray crystal structures. Absorption and emission spectroscopy, together with an electrochemical and UV-vis-NIR spectroelectrochemical investigation of the uncoordinated ligand and complexes, has been performed, highlighting a rather good luminescence efficiency and a poor bridge-mediated electronic communication between the metal centers of the dinuclear complexes. The electrogenerated chemiluminescence (ECL) of the dinuclear species has been explored, and for one of these, an exceptionally high ECL efficiency has been observed, comparable to that of [Ru(bpy)3]2+, which is considered a standard in ECL studies. [ABSTRACT FROM AUTHOR]

A novel methodology to prepare transparent luminescent hybrid materials is reported. Using a calixarene ionophore as a PMMA cross-linker avoids problems, such as phase segregation, and produces a polymer monolith that can be loaded with the metal ion required for luminescence post-synthesis. This approach is versatile and will simplify the production of such materials. [ABSTRACT FROM AUTHOR]

We demonstrate high-brightness and high-efficiency blue-green to yellow-green electrophosphorescent organic light-emitting diodes employing a series of organic Ir complexes [Ir-(C∧N)2(N∧N)]. Three different complexes have been synthesized showing high photoluminescence solid blend efficiencies up to 44%. A low current density increase of the electroluminescence (EL) external quantum efficiency (φEL(ext)) is observed and a maximum of φEL(ext)=10.6%±0.8% photon/e and power efficiency η=27±2 lm/W are achieved at a current density of j=0.01 mA/cm2. We examine various electronic processes that underlie a nonmonotonous current density dependence of the EL quantum efficiency of electrophosphorescent light-emitting diodes. The shape of φEL(ext) versus j is shown to reflect a trade off between electron-hole encounter and charge carrier transit times, electric field effect on electron-hole pair dissociation time, and current driven triplet molecular exciton lifetime. [ABSTRACT FROM AUTHOR]

Luminescent iridium tetrazolato complexes can be exploited for live cell imaging, and their cellular localization can be modulated by simple methylation of these neutral species to yield the corresponding cationic complexes. The neutral family of complexes displays a tendency to accumulate within the endoplasmic reticulum and, to a variable extent, lipid droplets. The analogous cationic complexes display a tendency to localize primarily in mitochondria. Interestingly, the neutral complexes highlight very low cytotoxicity when compared to their corresponding cationic species. More information can be found in the Full Paper S. E. Plush, D. A. Brooks, M. Massi et al. on page 15666. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of mixed ligand 2,2';6',2"-terpyridine (tpy) ruthenium complexes with 2,6-bis-([1,2,4]triazol-3-yl)pyridine, 2,6-bis(5-phenyl-[1,2,4]triazol-3-yl)pyridine, and 2,6-bis([1,2,3,4]tetrazol-5-yl)pyridine are reported. The species are characterized by HPLC, [sup1]H NMR, UV/vis, and emission spectroscopy. The photophysical properties of the complexes are investigated as a function of temperature over the range 80-320 K. The emission lifetime observed for the fully deprotonated compounds at room temperature is about 80 ns. This increase by 2 orders of magnitude with respect to the parent "[Ru(tpy)[sub2]][sup2+]" complex is rationalized by an increase in the energy of the metal based dσ orbital, rather than by manipulation of the π[sup*] orbitals on the ligands. The acid-base and electrochemical properties of the compounds are reported also. [ABSTRACT FROM AUTHOR]

One new set of triscarbonyl Re(I) diimine complexes with alkyl-tetrazoles as diimine-type ligands is described together with the study of their interaction with BSA. [Display omitted] • Cationic Re(I) tetrazole complexes. • Tetrazoles as diimine type ligands. • Luminescent Complexes. • Interaction with BSA. Herein, we report a new family of luminescent Re(I) complexes with general formula fac -[Re(diim)(CO) 3 L]0/+ in which the role of the diimine-type chelating ligand (diim) is played by alkylated tetrazoles. In particular, the design of the new complexes involved the choice of molecular scaffolds based on 2-pyridyl tetrazole (PTZ) and 2-quinolyl tetrazole (QTZ) which were decorated with various alkyl residues at N-2 position of the pentatomic ring, thereby endowing the resulting alkyl tetrazoles PTZ-R and QTZ-R with the proper "bpy-like" coordination attitude. As the "third" ligand (L), pyridine (pyr) or the 5-phenyl tetrazolato anion (Tph)− were selected, leading to cationic species such as fac -[Re(CO) 3 (PTZ-R)(pyr)]+, fac -[Re(CO) 3 (QTZ-R)(pyr)]+ and to the neutrally charged "fully tetrazole" complex fac -[Re(CO) 3 (QTZ-Me)(Tph)]. All the new complexes were identified by ESI-MS spectrometry and fully characterized by IR, 1H and 13C NMR spectroscopy. The findings that were suggested from the interpretation of the spectroscopic data were further confirmed by X-ray crystallography, with the analysis of the molecular structures of the cationic complexes fac -[Re(CO) 3 (PTZ-Me)(pyr)][PF 6 ] and fac -[Re(CO) 3 (QTZ-Me)(pyr)][PF 6 ]. Following the in-depth investigation of their photophysical properties, the new luminescent Re(I) tetrazole -based complexes were studied for any possible interaction with Bovine Serum Albumin (BSA). The results obtained from this preliminary screening highlighted that, along the series of the Re(I) tetrazole complexes, the QTZ-R based cationic derivatives fac- [Re(CO) 3 (QTZ-Me)(pyr)]+, fac- [Re(CO) 3 (QTZ- t Bu)(pyr)]+ , as well as the neutrally charged and "fully tetrazole" complex fac- [Re(CO) 3 (QTZ-Me)(Tph)], displayed the highest affinity to BSA. [ABSTRACT FROM AUTHOR]