Colorimetric azobenzene based chemosensors 1 and 2 were designed for detection of transition-metal ions such as Cu(II) under physiological pH conditions. The internal charge transfer (ICT) sensors are highly colored, absorbing in the green. For 1, the Cu(II) recognition gives rise to red-to-yellow color changes that are visible to the naked-eye and reversible upon addition of EDTA, whereas for 2, which lacks the aromatic o-methoxy chelating group, no such changes were observed.

The first examples of [Cu(N^N)(POP)](+) complexes (POP = bis(2-(diphenylphosphino)phenyl)ether) in which the N^N domain is a 2,2':6',2''-terpyridine (tpy) ligand have been prepared and characterized; N^N = tpy, 5,5''-dimethyl-2,2':6',2''-terpyridine (1), 4′-(4-tolyl)-2,2′:6′,2′′-terpyridine (2), 4′-(4-npropoxyphenyl)-2,2′:6′,2′′-terpyridine (3) and 4′-(4-nbutoxyphenyl)-2,2′:6′,2′′-terpyridine (4). In solution, the tpy domain in each [Cu(N^N)(POP)][PF6] complex is C2-symmetric, consistent with either tridentate coordination or a low energy dynamic process involving bidentate ligands; for [Cu(2)(POP)][PF6] and [Cu(4)(POP)][PF6], the (1)H NMR spectra showed negligible change between 295 and 210 K. The single crystal structures of [Cu(tpy)(POP)][PF6] and [Cu(4)(POP)][PF6] are presented. The asymmetric unit of [Cu(tpy)(POP)][PF6] contains two independent cations; in one the tpy ligand is tridentate and in the other, it is bidentate with the non-coordinated pyridine ring facing the Cu atom (Cu···N = 3.146(1) Å). In contrast, the solid-state structure of [Cu(4)(POP)][PF6] features a [Cu(4)(POP)](+) cation containing a bidentate tpy-domain with the non-coordinated pyridine ring oriented with the N-atom facing away from the Cu atom; this conformation may be associated with inter-cation NHC non-classical hydrogen bonds. The photophysical properties of [Cu(N^N)(POP)][PF6] with N^N = tpy or 1–4 are described. In the solid state at room temperature, the compounds are poorly emissive. In solution, the emission behaviour is consistent with ligand dissociation. This is supported by (1)H and (31)P NMR spectroscopic data which show POP and [Cu(POP)2](+) in solutions of aged samples; mass spectrometric data are consistent with the formation of [Cu(N^N)2](2+) in these samples.

The formation of a self-assembly between a sensitising antenna and an Eu(III) functionalised cyclen complex 1ÁEu, tethered to a gold surface via a C 12 alkyl thiol spacer, is described where changes in the Eu(III) emission signal the formation, and dissociation, of a ternary complex.The design and synthesis of functional material are of great current interest in chemistry and nanoscience. [1][2][3] In particular, systems based on the use of self-assembly formation have been developed and studied in solution as mimics of macroscopic devices such as molecular switches and sensors, integrated logic gates, and as artificial molecular machines.4-8 Immobilising such systems onto various solid substrates offers an attractive means of forming practical devices that possess more highly ordered and populated species than would generally be present in solution.9,10 The use of luminescence to investigate the properties and function of supramolecular assemblies has been extensively employed due to its non-invasive nature, fast response time and high sensitivity. 19,20 While the unique photophysical properties of the lanthanides make them ideal for observing self-assembly formation and for sensing, to the best of our knowledge, their use on gold substrates has not been achieved to date. Such modification would further increase their potential use in sensing applications, for instance, by combining them with atomic force microscope (AFM)-based micromechanical sensors, 21 which could result in the development of dual functioning sensory systems. We have previously demonstrated the formation of luminescent ternary complexes in solution formed through self-assembly using sensitising antennae and coordinatively unsaturated Eu(III) or Tb(III) complexes.22 Herein, we demonstrate that by anchoring such a lanthanide complex, 1ÁEu, onto a gold substrate, via an alkyl thiol linker, the lanthanide luminescence is 'switched on' upon formation of a self-assembly between 1ÁEu and a sensitising antenna, 2. The emission of this assembly can then be 'switched off' upon addition of 3, an anion possessing an antenna with unfavourable excited state energies for the population of the Eu(III) excited state.The rationale for our design is shown in Fig. 1. The gold substrates employed were made by firstly sonicating discs (9 mm diameter) of mica in ethanol, and then evaporating a thin layer of gold (approximately 10 nm). Following evaporation, the samples were immersed in 1 mM solutions of 1ÁEu and left overnight. This was followed by thoroughly rinsing the surface with ethanol and drying under N 2 .z Similarly, samples possessing 1ÁEu and 2 (1ÁEuÁ2) and 1ÁEu and the phosphate anion, flavin monophosphate 3 (1ÁEuÁ3), were also made for comparison purposes. The FTIR analysis of these modified gold surfaces showed the presence of both 1ÁEu and 1ÁEuÁ2 with a number of characteristic resonances being identified (see ESIw). For instance, the CQO stretch assigned to the carboxy amide of 1ÁEu appeared at 1624 cm À1 with a shoulder at 1636 cm À1, while the as...

We report the synthesis of copper(I) complexes of three ligands which contain a potential P,N,N,P-metal binding site. Elemental analysis confirms that the bulk products possess a composition of [CuL][PF6] where L = 1, 2 or 3. Electrospray mass spectrometry (ESI MS) provides evidence for speciation in MeCN or MeOH solutions and the formation of both [CuL]+ and [Cu2L2]2+; addition of NaCl to the ESI MS samples aids the observation of dinuclear species as [Cu2L2Cl]+ ions. NMR spectroscopic data for a CD3CN solution of [Cu(1)][PF6] were consistent with a mononuclear species, but more complex multinuclear spectra were observed for the same compound dissolved in CD2Cl2. In the solid state, dimeric species dominate. Crystals grown from CH2Cl2 solutions of [Cu(1)][PF6] are found to be [Cu2(1)2][PF6]2·6CH2Cl2; each Cu+ ion in the centrosymmetric cation is bound in an N,O,P,P-coordination sphere, the N-donor originating from the pyridine ring. In [Cu2(3)2][PF6]2, each bridging ligand in the centrosymmetric [Cu2(3)2]2+ ion acts as a P,N-chelate to each Cu+ ion. Competing with this dimeric assembly is that of a circular helicate in which each ligand 3 bridges adjacent pairs of copper(I) ions in a chiral, hexameric complex; both the Δ,Δ,Δ,Δ,Δ,Δ- and Λ,Λ,Λ,Λ,Λ,Λ-enantiomers are present in the crystal lattice; in [Cu6(3)6]6+, each ligand coordinates as a bis(P,N-chelate). The solution absorption spectra of [Cu(1)][PF6], [Cu(2)][PF6] and [Cu(3)][PF6] are dominated by ligand-based transitions and none of the copper(I) complexes exhibits emissive behaviour in solution.

ARTICLE This journal is © The Royal Society of Chemistry 2013J. Name., 2013, 00, 1-3 | 1 (1)