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Synthesis and characterization of Lewis base free coordination polymers of selected lanthanides are presented. For this purpose, the substituted Cot TIPS ligand (Cot TIPS = 1,4-bis-triisopropylsilyl-cyclo-octatetraendiide) was used to synthesize homoleptic, anionic multidecker compounds of the type [K{Ln III (ɳ 8 -Cot TIPS ) 2 }] n . Depending on the solvent used for crystallization and the ionic radii of the lanthanide cations, three different categories of one-dimensional heterobimetallic coordination polymers were obtained in the solid state. For the early lanthanides La and Ce a unique helical conformation was obtained by crystallization from toluene, while the ionic radius of Pr seems to be a turning point towards the crystallization of zigzag polymers. For Er a third structural motif, a trapezoidal wave polymer was observed. Additionally, the zigzag polymer for all compounds could be obtained by changing the solvent from toluene to Et 2 O, reavealing a correlation between solid-state structure and ionic radii as well as solvent. While photoluminescence (PL) properties of Cot-lanthanide compounds are scarce, the La complexes show ligand centered green luminescence, whereas the Ce complexes reveal deep red emission origin from d-f transitions. The Er-compounds are single-molecule magnets, in which the magnetic relaxation of each Er ion occurs isolated from its neighbors at temperatures above 10 K, while below 9 K a strong antiferromagnetic coupling between the Er ions was seen., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The synthesis of heteroleptic Cu(I) complexes with coumarin-functionalized aminodiphosphine and diimine ligands is described. The complexes show yellow to deep-red phosphorescence in the solid state at ambient temperature with quantum yields up to 21%. The emission color of the complexes can be tuned by systematic modifications in the ligand system.

Atomically precise nanomaterials with tunable solid-state luminescence attract global interest. In this work, we present a new class of thermally stable isostructural tetranuclear copper nanoclusters (NCs), shortly Cu 4 @oCBT, Cu 4 @mCBT and Cu 4 @ICBT, protected by nearly isomeric carborane thiols: ortho -carborane-9-thiol, meta -carborane-9-thiol and ortho -carborane 12-iodo 9-thiol, respectively. They have a square planar Cu 4 core and a butterfly-shaped Cu 4 S 4 staple, which is appended with four respective carboranes. For Cu 4 @ICBT, strain generated by the bulky iodine substituents on the carboranes makes the Cu 4 S 4 staple flatter in comparison to other clusters. High-resolution electrospray ionization mass spectrometry (HR ESI-MS) and collision energy-dependent fragmentation, along with other spectroscopic and microscopic studies, confirm their molecular structure. Although none of these clusters show any visible luminescence in solution, bright μs-long phosphorescence is observed in their crystalline forms. The Cu 4 @oCBT and Cu 4 @mCBT NCs are green emitting with quantum yields ( Φ ) of 81 and 59%, respectively, whereas Cu 4 @ICBT is orange emitting with a Φ of 18%. Density functional theory (DFT) calculations reveal the nature of their respective electronic transitions. The green luminescence of Cu 4 @oCBT and Cu 4 @mCBT clusters gets shifted to yellow after mechanical grinding, but it is regenerated after exposure to solvent vapour, whereas the orange emission of Cu 4 @ICBT is not affected by mechanical grinding. Structurally flattened Cu 4 @ICBT didn't show mechanoresponsive luminescence in contrast to other clusters, having bent Cu 4 S 4 structures. Cu 4 @oCBT and Cu 4 @mCBT are thermally stable up to 400 °C. Cu 4 @oCBT retained green emission even upon heating to 200 °C under ambient conditions, while Cu 4 @mCBT changed from green to yellow in the same window. This is the first report on structurally flexible carborane thiol appended Cu 4 NCs having stimuli-responsive tunable solid-state phosphorescence., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The versatile metalloligand [{HCCC(NDipp) 2 } 2 Au 2 ] (dipp = 2,6-diisopropylphenyl) was converted into early-late heterotetrametallic complexes [{ClCp 2 MCCC(NDipp) 2 } 2 Au 2 ] (M = Ti, Zr). These compounds show photoluminescence with either remarkably different (Ti) or similar (Zr) features as compared to related solely coinage metal containing acetylide amidinate complexes.

Reaction of the PNNP ligand system N , N '-bis[(2-diphenylphosphino)phenyl]formamidinate (dpfam) featuring different coordination compartments with [AuCl(tht)], [CuMes] 5 , [AgMes] 4 , or [AuC 6 F 5 (tht)] (tht = tetrahydrothiophene) resulted in tetranuclear homo- and heterometallic coinage metal complexes, as well as a hexanuclear gold complex. All of them feature a metal string conformation. Photophysical investigation revealed a significant dependence of the photoluminescence properties on the metal composition. Below 100 K, the PL efficiency of three compounds approaches nearly 100%.

A selective synthesis of bi- and trinuclear complexes featuring a tetradentate monoanionic PNNP ligand is presented. The binuclear coinage metal complexes show a typical fourfold coordination for Cu and Ag, which changes to a bifold coordination for Au. The latter is accompanied by an unusual charge separation. Optical properties are investigated using photoluminescence spectroscopy and complemented by time-dependent density-functional-theory calculations. All compounds demonstrate clearly distinguished features dependent on the metals chosen and differences in the complex scaffold.

A hexadeca-nuclear, N-heterocyclic carbene stabilized gold(i)-copper(i)-sulfido cluster is reported, which emits yellow-orange in the solid state. The nature of this emission is examined, supported by combined theoretical and spectroscopic studies.

A series of homo- and hetero-polynuclear coinage metal complexes based on a phosphine-substituted 1,2,3-triazole system is presented. Besides the P,N-ligand 1-benzyl-4-(diphenylphosphanyl)-1H-1,2,3-triazole (LPN), the P,C-donor ligand 1-benzyl-4-(diphenylphosphanyl)-3-methyl-1H-1,2,3-triazolium (LPCH+), featuring a potential mesoionic carbene moiety, was obtained by methylation of LPN. Starting from the monogold chloride complexes AuCl(LPN/LPC), the syntheses of a heterotrinuclear Au2Cu complex as well as a digold carbene complex are described. The multinuclear complexes show metallophilic interactions. Their photophysical properties were investigated by temperature-dependent photoluminescence (PL) measurements. In particular, the digold complex shows interesting PL properties including narrow exciton peaks arising in the excitation and emission spectra below 50 K. These might be related to the molecular 'chains' in the crystal structure of the digold complex, formed by phenyl ligand stacking.

The enantiomerically pure ligand P , P -diphenyl- N , N '-bis(( R )-1-phenylethyl)phosphinimidic amide ( 1 ; (R)-HPEPIA) was synthesized and subsequently deprotonated with alkali metal precursors to yield dimeric complexes [M 2 {(R)-PEPIA} 2 ] (M = Li ( 2 ), Na ( 3 ), K ( 4 ), Rb ( 5 )). The cesium compound [M{(R)-PEPIA}] ( 6 ) crystallized as a cocrystal composed of dimeric ([Cs 2 {(R)-PEPIA} 2 ] ( 6 d ) and 1D-polymeric ([Cs{(R)-PEPIA}] n ) ( 6 p ) species in a 1 : 1 ratio. The coordination polymer 6 p features a unique sinus-shaped configuration of repeating -Cs-N-P-N-Cs-N-P-N- units. Unusual photoluminescence (PL) properties were found for solid 1-6 : in contrast to the fluorescent ligand 1 , the alkali metal complexes show phosphorescence at low temperatures (<100 K) and thermally activated delayed fluorescence (TADF) above ∼150 K. The latter provides for PL quantum yields up to 36% ( 3 ) at ambient temperature. DFT calculations support that both 1 and 2-6 d have similar singlet and triplet excited states with energy separations of a few tens of meV. The strongly enhanced intersystem crossing (ISC) in the metal complexes, resulting in TADF, is attributed to their dimeric structure. This suggests that the fluorophore dimerization may serve as a tool to effect ISC for the design of TADF emitters.

To force metal ions in heterometallic coinage metal complexes into preset compartments, we have synthesized a ligand with two N-heterocyclic carbenes (NHCs) separated by a methylene bridge and two bipyridine moieties tethered to each NHC moiety. By using this ligand, tetranuclear heterodimetallic gold/copper and gold/silver complexes were obtained. These complexes show an unprecedented V-shape or linear MAu 2 M (M = Cu, Ag) configuration in the solid state. The photophysical properties of the new compounds are significantly affected by the complexed metal ions.

A heterotrinuclear [Pt 2 Fe] spin crossover (SCO) complex was developed and synthesized employing a ditopic bridging bpp-alkynyl ligand L and alkynyl coordinated Pt II terpy units: [Fe II (L-Pt II ) 2 ] 2 (BF 4 ) 2 (1). We identified two different types of crystals of 1 which differ in their molecular packing and the number of co-crystallized solvent molecules: 1H (1·3.5CH 2 Cl 2 in P1[combining macron]) and 1L (1·10CH 2 Cl 2 in C2/c); while 1L shows a reversible SCO with a transition temperature of 268 K, the analogous compound 1H does not show any SCO and remains blocked in the HS state. The temperature-dependent magnetic properties of 1H and 1L were complementarily studied by Mössbauer spectroscopy. It has been shown that 1L performs thermal spin crossover and that 1L can be excited to a LIESST state. The vibrational properties of 1 were investigated by experimental nuclear resonance vibrational spectroscopy. The experimentally determined partial density of vibrational states (pDOS) was compared to a DFT-based simulation of the pDOS. The vibrational modes of the different components were assigned and visualized. In addition, the photophysical properties of 1 and L-Pt were investigated in the solid state and in solution. The ultrafast transient absorption spectroscopy of 1 in solution was carried out to study the PL quenching channel via energy transfer from photoexcited Pt II terpy units to the Fe II -moiety.

The optical properties of four isostructural trinuclear chalcogenolato bridged metal complexes [Cu 2 Sn(SPh) 6 (PPh 3 ) 2 ], [Cu 2 Sn(SePh) 6 (PPh 3 ) 2 ], [Ag 2 Sn(SPh) 6 (PPh 3 ) 2 ] and [Cu 2 Ti(SPh) 6 (PPh 3 ) 2 ] have been investigated by absorption and photoluminescence spectroscopy and time-dependent density functional theory (TDDFT) calculations. All copper-tin compounds demonstrate near-infrared (NIR) phosphorescence at ∼900-1100 nm in the solid state at low temperature, which is nearly absent at ambient temperature. Stokes shifts of these emissions are found to be unusually large with values of about 1.5 eV. The copper-titanium complex [Cu 2 Ti(SPh) 6 (PPh 3 ) 2 ] also shows luminescence in the NIR at 1090 nm but with a much faster decay (τ ∼ 10 ns at 150 K) and a much smaller Stokes shift (ca. 0.3 eV). Even at 295 K this fluorescence is found to comprise a quantum yield as high as 9.5%. The experimental electronic absorption spectra well correspond to the spectra simulated from the calculated singlet transitions. In line with the large Stokes shifts of the emission spectra the calculations reveal for the copper-tin complexes strong structural relaxation of the excited triplet states whereas those effects are found to be much smaller in the case of the copper-titanium complex.

We report on the synthesis of tridentate-nitrogen pyrazole-pyridine-tetrazole (L(1)H) and pyrazole-pyridine-triazole (L(2)H) ligands and their complexation with lanthanides (Ln = Gd(iii), Eu(iii) and Tb(iii)) resulting in stable, charge-neutral complexes Ln(L(1))3 and Ln(L(2))3, respectively. X-ray crystallographic analysis of the complexes with L(1) ligands revealed tricapped trigonal coordination geometry around the lanthanide ions. All complexes show bright photoluminescence (PL) in the solid state, indicating efficient sensitization of the lanthanide emission via the triplet states of the ligands. In particular, the terbium complexes show high PL quantum yields of 65 and 59% for L(1) and L(2), respectively. Lower PL efficiencies of the europium complexes (7.5 and 9%, respectively) are attributed to large energy gaps between the triplet states of the ligands and accepting levels of Eu(iii). The triplet state energy can be reduced by introducing an electron withdrawing (EW) group at the 4 position of the pyridine ring. Such substitution of L(1)H with a carboxylic ester (COOMe) EW group leads to a europium complex with increased PL quantum yield of 31%. A comparatively efficient PL of the complexes dissolved in ethanol indicates that the lanthanide ions are shielded against nonradiative deactivation via solvent molecules.

Phenylpropynyl-functionalized imidazolium salts, as well as their gold complexes, were prepared in excellent yields affording suitable starting materials for metal cluster synthesis. The reactions of these gold complexes with coinage metal phenylacetylides [M(CCPh)](x) (M = Cu, Ag) resulted in the formation of novel heterometallic hexanuclear clusters which exhibit mixed metallophillic interactions and intense white photoluminescence at low temperature.

The synthesis, molecular structures and luminescence properties of two 'Cu12S6' cluster molecules with stabilizing bidentate phosphine ligands are described. Both display in the solid state at ambient temperature high photoluminescence quantum yields (≥48%) and good stability towards oxygen.

Reaction of a mixture of CuCl, PhSnCl(3) and PEt(2)Ph with S(SiMe(3))(2) in THF resulted initially in the unexpected synthesis of the ionic, mixed copper-tin sulfide cluster [Li(thf)(4)][Cu(19)S(28)(SnPh)(12)(PEt(2)Ph)(3)] in low yields. However, by adding NBu(4)Cl to the reaction solutions we were able to selectively synthesize the structurally similar cluster ion in (NBu(4))[Cu(19)S(28)(SnPh)(12)(PEt(2)Ph)(3)]. Structural characterization by single crystal X-ray analysis reveals that the cluster anions consist in principle of a copper sulfide core decorated by PhSn(3+) groups. Although additional phosphine ligands are attached to copper atoms the clusters possess an open 'Cu(3)S(3)' face mostly protected by the [Li(thf)(4)](+) and (NBu(4))(+) counterions in the crystal structure. The cluster (NBu(4))[Cu(19)S(28)(SnPh)(12)(PEt(2)Ph)(3)] displays near-infrared, temperature-dependent photoluminescence at ∼820-930 nm in the solid state, which is especially bright at temperatures below ∼100 K.

Two 2,6-bispyrazolylpyridine ligands (bpp) were functionalized with pyrene moieties through linkers of different lengths. In the ligand 2,6-di(1H-pyrazol-1-yl)-4-(pyren-1-yl)pyridine (L1) the pyrene group is directly connected to the bpp moiety via a C-C single bond, while in the ligand 4-(2,6-di(1H-pyrazol-1-yl)pyridin-4-yl)benzyl-4-(pyren-1-yl)butanoate (L2) it is separated by a benzyl ester group involving a flexible butanoic chain. Subsequent complexation of Fe(II) salts revealed dramatic the influence of the nature of the pyrene substitution on the spin-transition behaviour of the resulting complexes. Thus, compound [Fe(L1)(2)](ClO(4))(2) (1) is blocked in its high spin state due to constraints caused by a strong intermolecular π-π stacking in its structure. On the other hand, the flexible chain of ligand L2 in compounds [Fe(L2)(2)](ClO(4))(2) (2) and [Fe(L2)(2)](BF(4))(2)·CH(3)CN·H(2)O (3) prevents structural constraints allowing for reversible spin transitions. Temperature-dependent studies of the photophysical properties of compound 3 do not reveal any obvious correlation between the fluorescence of the pyrene group and the spin state of the spin transition core.

We have demonstrated a new strategy to synthesize Au mesocages using polyhedral Cu(2)O templates. The obtained polyhedral Au mesocages show a strong shape effect in highly sensitive single-particle surface-enhanced Raman spectroscopy (sp-SERS)., (© The Royal Society of Chemistry 2011)

Separation of single-walled carbon nanotubes (SWNT) by diameter is an important prerequisite for controlled experimental studies and efficient application of these systems. By comparing experimental data with molecular dynamics (MD) simulations, we demonstrate that water filling has a significant, tube-diameter dependent effect on the effective mass density of individual single-walled carbon nanotubes suspended in aqueous surfactant suspensions. We present a model for the effective density of the nanotube-surfactant complex in aqueous solution that permits a comprehensive description of its density across the entire, experimentally relevant range of SWNT diameters. Parameters for this model can be obtained from molecular dynamics simulations and/or experiment and help explain the subtle interplay of surfactant coverage and endohedral water in the separation of a particular diameter species of SWNT by gradient centrifugation.