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The Cu(i) complex of a pyridyl-tetrazolate ligand exhibits enhanced luminescence, which was fabricated as an OLED device with an EQE of 7.7%.

A new series of luminescent phosphine copper(I) complexes with cyano- and hydroxyl-substituted 2,2′-bipyridine ligands [CuI(bpy(CN)2)(P(PhX)3)2](ClO4) [X = H (1); Me (2); Cl (3)], [CuI(bpy(CN)2)(POP)](ClO4) (4), [CuI(bpy(OH)2)(PPh3)2](ClO4) (5) and [CuI(bpy(OH)2)(POP)](ClO4) (6) have been synthesized and characterized. Three of these complexes have been structurally characterized by using X-ray crystallography. The effect of the attaching –CN and –OH groups at the ortho-positions of bpy ligand was investigated. In CH2Cl2 solution, these complexes show yellow to orange phosphorescence, with the emission maxima not only sensitive to the electronic nature of the bipyridine ligands, but also considerably varied with the modification of phosphine ligands. In addition, these complexes show intense tunable green to yellow emissions in their solid state. To elucidate the electronic structures and transitions of these complexes, density functional theory (DFT) calculations on representative examples revealed that the lowest energy electronic transition associated with these complexes predominantly originates from metal-to-ligand charge transfer transitions (MLCT).

The photocatalytic generation of an NADH synthetic analogue, i.e. 1-benzyl-1,4-dihydronicotinamide (1,4-BNAH), has been studied using the cobalt diimino–dioxime complexes and the BF2-bridged derivative as catalysts. 1,4-BNAH was produced in both aqueous and organic media at unprecedented turnover numbers with metal and organic photosensitizers, respectively.

Artificial photosynthesis is considered as one of the most promising strategies for solar-to-fuel conversion through sunlight-driven water splitting and CO2 reduction. This tutorial describes recent developments in the use of metal quaterpyridine complexes as electrocatalyts and photocatalysts for artificial photosynthesis.

Nitrogen oxide (NO

A series of blue-green emitting RuII diisocyano complexes containing 2-benzoxazol-2-ylphenolate (PBO) have been prepared. The complexes were isolated under varied reaction conditions in two isomeric forms, i.e., trans,trans,trans- (1) and cis,trans,cis- (2), with varied ligand coordination geometry above the RuII center. The photoluminescence of the isomeric complexes has been compared and tuned by the systematic variation of the electronic properties of the isocyanides. The cis,trans,cis- isomers exhibit structureless emission in the blue-green region (471-517 nm) upon excitation at λex > 400 nm in dichloromethane solution at room temperature. Both isomeric forms show similarly structured greenish emission at 499-523 nm on excitation at λex > 355 nm in a methanol/ethanol (4:1) glassy medium at 77 K. On careful comparison with the corresponding absorption and electrochemical data, it is suggested that the solution emission of the cis,trans,cis- isomers (2) at room temperature is originated from the metal-to-ligand charge transfer (MLCT), while a ligand-centered (LC) parentage is assigned for the emission in a glassy state for both isomeric forms. In line with the above experimental results, DFT calculation demonstrates the change in the nature and relative energy of the HOMOs and LUMOs with respect to the varied ligand coordination geometry and π-accepting ability of the isocyanides.

Sea lice (Copepoda: Caligidae) are ectoparasites which negatively impact marine aquaculture species around the world. There are a limited number of treatments licensed for use against sea lice in tropical and semi-tropical farmed fish species. Emamectin benzoate (EB) was an effective pharmaceutical drug against sea lice infestations in several salmon industries before resistance to the product developed. This drug has not been extensively tested in marine fish within Asia. The objective of this study was to determine whether this drug could be used to treat oral infections with sea lice in hybrid grouper (Mycteroperca tigris × Epinephelus lanceolatus) cultured in saltwater net-pen sites in Hong Kong. We observed an overall reduction in sea lice infections over time, starting on the last day of the treatment up to the end of our study (i.e., 14 days after the last EB treatment). We also observed a large variation in concentrations of EB in fish on the last day of the treatment, which provides an explanation for the variation in response to the treatment. It also suggests that distribution of the medication to fish in saltwater net-pens is difficult, especially when medication is hand-mixed in the feed and possibly unevenly distributed in the daily rations. Overall, this study provides preliminary evidence that EB could be used to treat sea lice found in Hong Kong and potentially in other regions of SE Asia.

Luminescent Pb2+-based metal–organic frameworks (MOFs) belong to a new class of multifunctional molecular materials with interesting luminescence properties and potential applications within a single crystalline phase. In this mini review, we present the recent advances that have been achieved in their applications as single-phase white-light emitting materials and chemosensors in the last decade. We focus on the trends in the modification of their structures and luminescence by various bridging ligands, and subsequently their multifunctional applications, which may affect the future development of the field.

Artificial photosynthesis is considered as one of the most promising strategies for solar-to-fuel conversion through sunlight-driven water splitting and CO2 reduction. This tutorial describes recent developments in the use of metal quaterpyridine complexes as electrocatalyts and photocatalysts for artificial photosynthesis.

The visible light-driven catalytic water reduction by a cobalt(II) tripodal iminopyridine complex [Co(tachpy3)](ClO4)2 (1) (tachpy3 = cis,cis-1,3,5-tris(pyridine-2-carboxaldimino)-cyclohexane) has been investigated in aqueous acetonitrile. The catalysis is found to be homogeneous and an impressive H2 TON of 16 440 has been achieved, which is far better than that by a structurally related complex [Co(trenpy3)](ClO4)2 (2) (trenpy3 = tris-[4-(2-pyridyl)-3-azabut-3-enyl]amine) bearing identical donor groups. A comparison between the two complexes reveals that the catalytic properties are sensitive to the change in ligand rigidity and thus the coordination geometry, as reflected by their respective reaction potentials and H2 TONs. The catalysis of 1 proceeds via a penta-coordinate species formed by the protonation of the corresponding CoI state. The results in spectroscopic and electrochemical studies are supplemented by DFT computation.

The invention of efficient systems for the photocatalytic reduction of CO2 comprising earth-abundant metal catalysts is a promising approach for the production of solar fuels. One bottleneck is to design highly selective and robust molecular complexes that are able to transform the CO2 gas. The CuII quaterpyridine complex [Cu(qpy)]2+ (1) is found to be a highly efficient and selective catalyst for visible-light driven CO2 reduction in CH3CN using [Ru(bpy)3]2+ (bpy: bipyridine) as photosensitizer and BIH/TEOA (1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole/triethanolamine) as sacrificial reductant. The photocatalytic reaction is greatly enhanced by the presence of H2O (1–4 % v/v), and a turnover number of >12 400 for CO production can be achieved with 97 % selectivity, which is among the highest of molecular 3d CO2 reduction catalysts. Results from Hg poisoning and dynamic light scattering experiments suggest that this photocatalyst is homogenous. To the best of our knowledge, 1 is the first example of molecular Cu-based catalyst for the photoreduction of CO2.

This study adopted a researcher-generated framework to analyze STEM activities demonstrated in primary students’ science projects in an annual extracurricular event held in Hong Kong. Ten students’ project reports were randomly selected from each of the three groups of 24 outstanding, 45 merit, and 68 consolation awarded projects. Content analysis was conducted to code the activities in each project. The coded information was then changed into numerical data for quantitative analysis. The results showed that, in general, more engineering and science activities than technology and mathematics activities were adopted by the primary students in their projects. More projects with the Outstanding Award conducted STEM activities than those projects with Merit and Consolation Awards, and significant group differences existed in the science and mathematics activities. Besides, science activities significantly positively related to engineering and mathematics activities. Furthermore, STEM-related content knowledge of discipline core ideas and crosscutting concepts were reported. This study sheds light on the pattern of STEM activities in students’ science projects, and has implications for promoting STEM integration in primary education.

A series of triphenylphosphine Cu(I) complexes with various diimine ligands, [Cu(N–N)(PPh3)2](ClO4) [N–N = dmp (2); Ph2Phen (3); Ph2dmp (4); dpq (5); dppz (6); phenCN (7); phenOH (8)] are synthesized by the ligand substitution reactions of [Cu(MeCN)4](ClO4) with 2 mole equiv. of PPh3 ligand and 1.2 mole equiv. of diimine ligand. {Cu(dpq)[P(XPh)3]2}(ClO4) [X = Me (5a); OMe (5b); Cl (5c)] and {Cu(phenOH)[P(XPh)3]2}(ClO4) [X = Me (8a); OMe (8b)] are also obtained by using various substituted phosphine ligands. These mixed-ligand complexes have been characterized using 1H and 31P NMR spectroscopy, IR spectroscopy, mass spectrometry and elemental analysis. Three of these complexes have been structurally characterized by X-ray crystallography. The photophysical and electrochemical properties of these complexes have been studied. These complexes exhibit MLCT phosphorescence with emission energy, lifetimes and quantum yields showing strong dependence on the nature of diimine and phosphine ligands. In particular, both the electronic and steric effects of the substituting groups in phosphine ligands are also found to affect the emission properties of the complexes. Our study provides structural-properties information for the future design of luminescent Cu(I) complexes.

In this paper, the energy levels of Yb 3+ ions in yttrium aluminum borate (YAB) crystal were calculated from a first-principles approach with an optimized defect structure obtained from the WIEN2k package and a traditional fitting method using a more reliable computer package. The calculated results were then compared with those obtained from a re-calculation using the values of parameters given by some previous researchers. Three types of likely mistakes in the previous researcher's paper, namely over fitting, incorrect use of irreducible representation, and errors in the calculations for the EPR parameters were clearly identified and effectively rectified in this paper. The electron paramagnetic resonance (EPR) parameters, which included g factors like g // and g ⊥ and hyperfine structure constants A // and A ⊥ , were also calculated through the perturbation method and compared with some observed values available in literature. There was reasonable agreement found with the experimental values which lay between the values obtained from the first-principles calculation ( g // =4.000 and g ⊥ =1.391; A // =1032 and A ⊥ =360 in 10 −4 cm −1 for 171 Yb 3+ ) and those from the fitting approach ( g // =3.612 and g ⊥ =1.702; A // =867 and A ⊥ =470 in 10 −4 cm −1 for 171 Yb 3+ ).

A series of cyano-bridged homotrinuclear Re(I) complexes with the general formula of {[Re]′[Re][Re]′}+ {[Re]′ = −[ReI(CO)2(LL)(X)]; [Re] = −[(NC)ReI(CO)2(phen)(CN)]–; LL = diimine, diphosphine, or two carbonyl ligands; X = triphenylphosphine or carbonyl ligand} and the corresponding mononuclear complex analogues were synthesized. The structures of most of the trinuclear Re(I) complexes have been determined by X-ray crystallography. The relative orientations of peripheral to central Re(I) units in these structures vary considerably. The photophysical properties of these trinuclear Re(I) complexes have been examined. Except for the trinuclear Re(I) complex with Br2phen ligand, all the other triads display orange to red photoluminescence derived from the 3MLCT [dπ(Re) → π*(phen)] origin of the central Re(I) unit, suggestive of efficient energy transfer between the peripheral chromophores and the central unit. In addition to the efficient energy transfer processes between the Re(I) chromophores in these trinu...

The reactions of [RuII(SQ)2(PPh3)2] (SQ = quinoline-8-thiolate) with different isocyanide ligands affords a series of emissive bis(quinoline-8-thiolate) ruthenium(II) complexes [RuII(SQ)2(PPh3)(CNR)] (1–6). Two isomeric forms, i.e. cis,trans (1a – 6a) and cis,cis (1b – 6b) have been separated in these reactions. With the variation on the π-accepting ability of the isocyanide ligands, the CN stretches, lowest energy absorptions and the photoluminescence can be systematically modified.

Luminescent porous coordination polymers, cage-containing chains [Pb5(L1)6(N3)2(OH)2]n (1) and 1-D double helical chains [Pb(L2)(N3)]n (2) with 1-D channels were prepared by solvothermal reactions.

A series of polynuclear metal complexes, [Cu2(L1)(PPh3)4](ClO4)2 (1), [Cu3(L2)(PPh3)6](ClO4) (2), [Cu3(L3)(PPh3)6] (3), [Ag2(L1)(PPh3)4](BF4)2 (4), [Ag4(L2)2(PPh3)6] (5) and [Ag3(L3)(PPh3)5] (6), have been obtained from the reactions of the highly conjugated bridging ligands 2,3-bis(2-pyridyl)pyrazine (L1), 2,3-bis(2-tetrazoyl)pyrazine (H2L2) and 2,3-bis(2-tetrazoyl)imidazole (H3L3) with [Cu(MeCN)4]ClO4 and AgBF4, respectively. Their crystal structures have been determined by X-ray crystallography and their photophysical properties have been investigated in detail. Complexes 1 and 3 show photoluminescence in CH2Cl2 solution, while all the complexes exhibit obvious luminescence in the solid state; detailed photophysical studies and density functional theory calculations of these complexes have revealed that their lowest energy absorptions and emissions are predominantly derived from either metal-to-ligand charge-transfer (MLCT) or intraligand (IL) excited states.

A series of homoleptic mononuclear 8-coordinate FeII and CoII compounds, [FeII(L2)2](ClO4)2 (2), [FeII(L3)2](ClO4)2 (3), [FeII(L4)2](ClO4)2 (4), [CoII(L1)2](ClO4)2 (5), [CoII(L2)2](ClO4)2 (6), [CoII(L3)2](ClO4)2 (7), and [CoII(L4)2](ClO4)2 (8) (L1 and L2 are 2,9-dialkylcarboxylate-1,10-phenanthroline ligands; L3 and L4 are 6,6′-dialkylcarboxylate-2,2′-bipyridine ligands), have been obtained, and their crystal structures have been determined by X-ray crystallography. The metal center in all of these compounds has an oversaturated coordination number of 8, which is completed by two neutral homoleptic tetradentate ligands and is unconventional in 3d-metal compounds. These compounds are further characterized by electronic spectroscopy, cyclic voltammetry (CV), and magnetic measurements. CV measurements of these complexes in MeCN solution exhibit rich redox properties. Magnetic measurements on these compounds demonstrate that the observed single-ion magnetic (SIM) behavior in the previously reported [FeII(L1)2...

The invention of efficient systems for the photocatalytic reduction of CO

A series of nickel(II) complexes bearing tetradentate macrocyclic N4, N3S, and N3P ligands were synthesized, and their photocatalytic activity toward proton reduction has been investigated by using [Ir(dF(CF3)ppy)2(dmbpy)]PF6 (dF(CF3)ppy = 2-(2,4-difluorophenyl)-5-trifluoromethylpyridine and dmbpy = 4,4′-dimethyl-2,2′-dipyridyl) as the photosensitizer and triethylamine (TEA) as the sacrificial reductant. The complex [Ni(L4)]2+ (L4 = 2,12-dimethyl-7-phenyl-3,11,17-triaza-7-phospha-bicyclo[11,3,1]heptadeca-1(17),13,15-triene), which bears a phosphorus donor atom, shows the highest efficiency with TON up to 5000 under optimized conditions, while the tetraaza macrocyclic nickel complexes [Ni(L1)]2+ and [Ni(L2)]2+ (L1 = 2,12-dimethyl-3,7,11,17-tetra-azabicyclo[11.3.l]heptadeca-1(17),2,11,13,15-pentaene; L2 = 2,12-dimethyl-3,7,11,17-tetra-azabicyclo[11.3.l]heptadeca-1(17),13,15-triene) show lower photocatalytic activities. Transient UV–vis absorption and spectroelectrochemical experiments show that Ni(II) is re...

Processes for the conversion of CO2 to valuable chemicals are highly desired as a result of the increasing CO2 levels in the atmosphere and the subsequent elevating global temperature. However, CO2 is thermodynamically and kinetically inert to transformation and, therefore, many efforts were made in the last few decades. Reformation/hydrogenation of CO2 is widely used as a means to access valuable products such as acetic acids, CH4, CH3OH, and CO. The electrochemical reduction of CO2 using hetero- and homogeneous catalysts recently attracted much attention. In particular, molecular CO2 reduction catalysts were widely studied using transition-metal complexes modified with various ligands to understand the relationship between various catalytic properties and the coordination spheres above the metal centers. Concurrently, the coupling of CO2 with various electrophiles under homogeneous conditions is also considered an important approach for recycling CO2 as a renewable C-1 substrate in the chemical industry. This review summarizes some recent advances in the conversion of CO2 into valuable chemicals with particular focus on the metal-catalyzed reductive conversion and functionalization of CO2.

The effects of KOH concentration (10–30 M) on the morphology of KNbO 3 produced from Nb 2 O 5 by hydrothermal synthesis have been investigated. High purity KNbO 3 nanocubes have been obtained using 30 M KOH at 200 °C. The KNbO 3 nanocubes can be readily doped with nitrogen by heating with urea at 425 °C without significant change in morphology. The band gap of KNbO 3 decreases from 3.13 to 2.76 eV as a result of N-doping, the surface area also increases substantially. The photocatalytic activity of the N-doped KNbO 3 nanocubes has been evaluated by photodegradation of four organic contaminants (rhodamine B, orange G, bisphenol A and pentachlorophenol) as well as water splitting under visible light irradiation. The results show that the photocatalytic activity of N-doped KNbO 3 is significantly higher than that of pure KNbO 3 nanocubes and Degussa TiO 2 P25 under visible light irradiation.

Luminescent porous coordination polymers, cage-containing chains [Pb

Reaction of [RuII(PR3)3Cl2] with 2-methyl-8-quinolinolate (MeQ) in the presence of Et3N in MeOH produced the neutral carbonyl hydrido complexes [RuII(MeQ)(PR3)2(CO)(H)] (R = Ph (1), MeC6H4 (2), MeO...

The species cis-[RuII(2,9-Me2phen)2(OH2)2]2+, both in homogeneous solution and supported on Dowex cation-exchange resin, is a highly active and robust catalyst for the oxidation of alcohols and alkenes in water at room temperature, using Ce(IV) and IO4– as terminal oxidants, with a turnover number (TON) of >104.

The cobalt(III) macrocyclic Schiff-base complex, [CoIII(CR)Cl]ClO4 (CR = 2,12-dimethyl-3,7,11,17-tetra-azabicyclo[11.3.1]-heptadeca-1(17),2,11,13,15-pentaene), is an active catalyst for the electrocatalytic proton reduction to generate dihydrogen in both acetonitrile and 100% aqueous solution (at −0.57 and −0.85 V vs SCE, respectively), using p-cyanoanilinium tetrafluoroborate and acetic acid as proton sources, respectively. Bulk electrolysis confirmed that dihydrogen is produced with >90% Faradaic yields and >50 TON in both solvents. [CoIII(CR)Cl2]ClO4 also catalyzes photo-driven (λ > 390 nm) hydrogen production in aqueous acetonitrile at TON of 180 (not optimized), using [IrIII(ppy)2(bpy)]PF6 as the photosensitizer, triethanolamine (TEOA) as the sacrificial donor and acetic acid as the proton source.

Nitrogen doped K2Nb4O11 (K2Nb4O11-N) has been prepared by solid state reaction between K2Nb4O11 and urea at 400 °C. K2Nb4O11-N has been characterized by XRD, SEM, XPS and UV/vis diffuse reflectance. The photodegradation of various organic pollutants in water by this material, including Orange G (OG), bisphenol A (BPA) and pentachlorophenol (PCP) have been studied at λ > 330 nm and >399 nm. The results show that the photocatalytic activity of K2Nb4O11-N at >399 nm is higher than those of K2Nb4O11 and Degussa TiO2 P25, indicating the activating effect of nitrogen doping. A mechanism for the photodegradation of organic substrates by K2Nb4O11-N is proposed.

A polypyridyl ruthenium(II) complex, cis-[RuII(2,9-Me2phen)2(H2O)2]2+, has been adsorbed onto the cation-exchange resins Dowex-50W and Chelex-100. The potential use of the supported ruthenium(II) complex as catalyst for the oxidative degradation of organic pollutants in water has been investigated using bisphenol A, an emerging endocrine disruptor, as substrate; and the environmentally friendly H2O2 as oxidant. These solid-supported catalysts are found to be efficient for the degradation of bisphenol A in aqueous solution by H2O2 under ambient conditions. The intermediates and products formed during the oxidative degradation of bisphenol A by these catalytic systems have been identified and a mechanism is proposed. The supported catalysts are easily recovered by simple filtration and display no loss of activity when recycled.

A series of ruthenium(II) bis(8-quinolinolato) complexes bearing isocyanide ligands (RNC) have been synthesized by the reaction of [RuQ3] (Q = 8-quinolinolate) with RNC in the presence of Zn/Hg. These complexes have the general formula [RuQ2(RNC)2] (1, R = tert-butyl; 2, R = 4-MeOPh; 3, R = 4-ClPh; 4, R = 2,4,6-Br3Ph). Both the yellow cis,cis,trans (a) and orange-red trans,trans,trans (b) isomers have been isolated for complexes 1−4. trans,trans,trans-[Ru(Tol-Q)2(tBuNC)2] (6, HTol-Q = 8-hydroxyl-5-tolylquinoline) has also been prepared from [Ru(PPh3)2Cl2]. The structures of 2a, 3a, and 4b have been determined by X-ray crystallography. These complexes exhibit an intense absorption band in the UV region (λmax = 320−390 nm) with molar extinction coefficients (e) on the order of 104 dm3 mol−1 cm−1 and a moderately intense absorption with e on the order of 103 dm3 mol−1 cm−1 at 400−492 nm. The intense absorption at 320−390 nm is assigned to the ligand-centered π→π* transitions of the quinolinolate ligands, pro...

A series of osmium(VI) nitrido complexes containing pyridine-carboxylato ligands OsVI(N)(L)2X (L = pyridine-2carboxylate (1), 2-quinaldinate (2) and X = Cl (a), Br (1b and 2c) or CH3O (2b)) and [OsVI(N)(L)X3]− (L = pyridine-2,6-dicarboxylate (3) and X = Cl (a) or Br (b)) have been synthesised. Complexes 1 and 2 are electrophilic and react readily with various nucleophiles such as phosphine, sulfide and azide. Reaction of OsVI(N)(L)2X (1 and 2) with triphenylphosphine produces the osmium(IV) phosphiniminato complexes OsVI(NPPh3)(L)2X (4 and 5). The kinetics of nitrogen atom transfer from the complexes OsVI(N)(L)2Br (2c) (L = 2-quinaldinate) with triphenylphosphine have been studied in CH3CN at 25.0 °C by stopped-flow spectrophotometric method. The following rate law is obtained: −d[Os(VI)]/dt = k2[Os(VI)][PPh3]. OsVI(N)(L)2Cl (L = 2-quinaldinate) (2a) reacts also with [PPN](N3) to give an osmium(III) dichloro complex, trans-[PPN][OsIII(L)2Cl2] (6). Reaction of OsVI(N)(L)2Cl (L = 2-quinaldinate) (2a) with lithium sulfide produces an osmium(II) thionitrosyl complex OsII(NS)(L)2Cl (7). These complexes have been structurally characterised by X-ray crystallography.

Reduction of RuQ3 (1a, Q = 8-quinolinolato) with Zn/Hg in the presence of various π-acceptor ligands in ethanol affords RuQ2L2 (L2 = (dimethylsulfoxide)2 (2); (4-picoline)2 (3); N,N′-dimethyl-1,4-diazabuta-1,3-diene, dab (4); cyclooctadiene, COD (5); norborna-2,5-diene, nbd (6)). Compound 6 is isolated as an equimolar mixture of cis,trans (6a) and trans,cis (6b) isomers, which can be separated by column chromatography. DFT calculations have been performed on 6a and 6b. Oxidation of 3 and 6b affords the corresponding ruthenium(III) species 7 and 8, respectively. The structures of 2, 3, 4 and 6 have been determined by X-ray crystallography.

A series of osmium(VI) nitride complexes containing 8-quinolinolato ligands, [OsVI(N)(X-Q)2Cl] (X = H, 5-Cl, 5-NO2, 2-Me; 1a–d), have been synthesized by reaction of HX-Q with [nBu4N][OsVI(N)Cl4] in the presence of 2,6-dimethylpyridine. The ν(Os≡N) stretches of these compounds occur at 1056–1075 cm–1, and are within the range (1050–1120 cm–1) found for most osmium nitride species. The structure of 1d has been determined by X-ray crystallography. The osmium center adopts a distorted octahedral geometry, and the two quinolinolato ligands are cis to each other. The three N atoms are in a facial arrangement, and the Os≡N bond distance is 1.644(6) A. Complex 1c readily reacts with the carbene precursors bis(1,3-dialkylimidazolidin-2-ylidene) (LR2; R = Me, Et, or CH2Ph) to produce the osmium(IV) azavinylidene species, [OsIV(N=LR)(NO2-Q)2Cl], which are derived from the formal addition of the carbenes LR to OsVI≡N. The structure of [OsIV(N=LEt)(NO2-Q)2Cl] (2b) has been determined by X-ray crystallography. The osmium center has a distorted octahedral geometry in which the facial arrangement of the three N atoms is retained. The Os(1)–N(5) distance of 1.875(6) A is rather long and, together with the rather acute Os(1)–N(5)–C(19) angle of 133.8(5)°, indicates that there is no significant multiple-bond character in the Os(1)–N(5) bond. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Treatment of AgNO3 with a tetrazolyl ligand H2L1 afforded a 3-D coordination polymer [Ag2(L1)]n (1). The crystal structure was determined by X-ray crystallography and it shows that both Ag1 and Ag2 atoms in the asymmetric unit exhibit distorted tetrahedron geometries, which are modified by Ag⋯Ag interactions. The flexible methylene –CH2– linkage between tetrazolate and phenyl ring effectively reduces the steric strain in the resultant 3D-framework. L1 exhibits an unsual coordination mode in which all nitrogen atoms in the two tetrazolato units are coordinated to the AgI centers. The luminescent property of 1 was also investigated. It exhibits multiple emission bands; the high energy emission band is assigned to the ligand-centered π⋯π transition, while the low energy emission bands are tentatively assigned to ligand-to-metal charge transfer (LMCT) that are modified by Ag⋯Ag interaction. The independence of the chromaticity coordinates of 1 on the excitation wavelength also suggests that it is a potentially useful single–component white-light-emitting material.

This paper presents some preliminary quantitative findings on the characteristics of business cycles in Hong Kong. The recently developed “approximate bandpass filter” is used to extract the fluctuations at business cycle frequencies (8 to 32 quarters) of macroeconomic time series. Based on the filtered time series, the paper identifies the cyclical turning points, describes the pattern of output fluctuations, and examines the co-movement of various macroeconomic variables.