Solvent effect on the linkage isomerism in [Fe(CO)4(NCS)]− and [Fe(CO)4(SCN)]− anions: A theoretical investigation

The present study illustrated the stability of linkage isomers of [Fe(CO)₄(NCS)]^? and [Fe(CO)₄(SCN)]^? by the use of PBE quantum method. It also investigated the polarity of solvent effect on dipole moment, structural parameters, and frontier orbital energies of complexes. The results indicated that the polarity of solvent had a significant effect on the frontier orbital energies and HOMO-LUMO gap. The character of Fe-C bonds of molecules was analyzed by Natural bond orbital (NBO) analysis. Back-bonding effect in these bonds was explored with calculation of quadrupole polarization of carbon atom by QTAIM analysis. Also, ¹⁴N NQR parameters were used for the illustration of Fe-NCS and Fe-SCN bonds.     

Multifunctional iron thiocarboxylate complexes: synthesis,reactivity and structure of CpFe(CO)<Subscript>2</Subscript>SCO-3,5-C<Subscript>6</Subscript>H<Subscript>4</Subscript>(COCl)<Subscript>2</Subscript>

A controlled substitution reaction of the chlorine atoms of 1,3,5-benzenetricarbonyl trichloride by the organoiron fragment (CpFe(CO)₂S) has been achieved. The complexes CpFe(CO)₂SCO-3,5-C₆H₃(COCl)₂ (1), 1,3-[CpFe(CO)₂SCO]₂-5-C₆H₃COCl (2) and 1,3,5-[CpFe(CO)₂SCO]₃C₆H₃ (3) were prepared from the reaction of (μ-S _x )[CpFe(CO)₂]₂ (x = 3, 4) with 1,3,5-C₆H₃(COCl)₃ in a 1:1, 2:1, or 3:1 metal to ligand molar ratio. The reactions of (1) with amines, thiols, and carboxylic acids produce the trifunctional mono-iron complexes CpFe(CO)₂SCO-3,5-C₆H₃(COY)₂ [Y = NR₂ (4), SR (5), OCOR (4)]. The X-ray structure determination of (1) is reported.     

Metal-metal bond cleavage in [Cp(CO)<Subscript>2</Subscript>Fe-Fe(CO)<Subscript>2</Subscript>Cp] under the action of organotellurium(IV)tribromides

The oxidation of [CpFe(CO)₂]₂ by RTeBr₃ allowed the corresponding organotellurodibromide complexes CpFe(CO)₂TeBr₂R (R=Ph, cyclo-(C₈H₁₂)(OMe). Their structural features (as determined by single-crystal X-ray diffraction analysis) are discussed.     

Synthesis,Structure and Isomerism of the [Fe<Subscript>3</Subscript>Pt(μ<Subscript>4</Subscript>-Q)(CO)<Subscript>9</Subscript>(dppm)] Clusters (Q = Se,Te; dppm = Ph<Subscript>2</Subscript>PCH<Subscript>2</Subscript>PPh<Subscript>2</Subscript>)

The reaction of K₂[Fe₃(μ₃-Q)(CO)₉] (Q = Se (K₂[1a]), Te (K₂[1b])) with [(dppm)PtCl₂] leads to the addition of a [(dppm)Pt]²⁺ unit to a Fe₂Q face of the initial cluster. By this way new heteronuclear clusters [Fe₃Pt(μ₃-Q)(CO)₉(dppm)] were obtained possessing a butterfly-shaped cluster core bridged by a μ₄-Q unit. It has been found that the resulting Fe-Pt clusters exist as equilibrium mixtures of two isomeric forms in solution differing by the dppm coordination mode: as a chelate ligand coordinated to Pt or as a bridging ligand coordinated to Pt and Fe atoms. The mixtures of isomers can be separated by chromatography and the pure isomers can be isolated as stable crystalline phases. Solutions of both isomers attain equilibrium at normal conditions in about 1 month as found by NMR. Dedicated to Professor Dieter Fenske in the occasion of his 65th birthday.     

Capping [H<Subscript>8−n</Subscript>Ni<Subscript>42</Subscript>C<Subscript>8</Subscript>(CO)<Subscript>44</Subscript>]<Superscript>n−</Superscript> (n = 6, 7, 8) Octa-carbide Carbonyl Nanoclusters with [Ni(CO)] and [CuCl] Fragments

The reactions of [Ni₁₆(C₂)₂(CO)₂₃]^4? and [Ni₃₈C₆(CO)₄₂]^6? with CuCl afforded mixtures of the previously reported [HNi₄₂C₈(CO)₄₄(CuCl)]^7? bimetallic octa-carbide cluster and the new [HNi₄₃C₈(CO)₄₅]^7? and [HNi₄₄C₈(CO)₄₆]^7? homo-metallic octa-carbides. The three species have very similar properties resulting always in co-crystals such as [NMe₄]₇[HNi_42+2xC₈(CO)_44+2x(CuCl)_1?x]·6.5MeCN (x = 0.14) (86% [HNi₄₂C₈(CO)₄₄(CuCl)]^7?, 14%[HNi₄₃C₈(CO)₄₅]^7?/[HNi₄₄C₈(CO)₄₆]^7?) and [NMe₄]₇[HNi_42+2xC₈(CO)_44+2x(CuCl)_1?x]·5.5MeCN (x = 0.30) (70% [HNi₄₂C₈(CO)₄₄(CuCl)]^7?, 30% [HNi₄₃C₈(CO)₄₅]^7?/[HNi₄₄C₈(CO)₄₆]^7?). The new homo-metallic octa-carbides can be obtained free from the Ni–Cu octa-carbido cluster by reacting [Ni₁₀(C₂)(CO)₁₆]^2? in thf with a stoichiometric amount of CuCl, and crystals of [NMe₄]₆[H₂Ni_43+xC₈(CO)_45+x]·6MeCN (x = 0.72), which contain [H₂Ni₄₄C₈(CO)₄₆]^6? (72%) and [H₂Ni₄₃C₈(CO)₄₅]^6? (28%), have been obtained. Despite the different charges and compositions, these anions display almost identical structures, which are also closely related to those previously reported for the bimetallic Ni–Cd octa-carbido clusters [Ni_42+xC₈(CO)_44+x(CdCl)]^7? and [HNi_42+xC₈(CO)_44+x(CdBr)]^6?. Indeed, all these clusters are based on the same Ni₄₂C₈ cage decorated by miscellaneous [CdX]⁺ (X = Cl, Br), [CuCl] and [Ni(CO)] fragments.     

Thermal study of cyclopalladated complexes of the type [Pd<Subscript>2</Subscript>(dmba)<Subscript>2</Subscript>X<Subscript>2</Subscript>(bpe)]

The synthesis, characterization and thermal analysis of the novel cyclometallated compounds [Pd₂(dmba)₂Cl₂(μ-bpe)] (1), [Pd₂(dmba)₂(N₃)₂(μ-bpe)] (2), [Pd₂(dmba)₂(NCO)₂(μ-bpe)] (3), [Pd₂(dmba)₂(SCN)₂(μ-bpe)] (4), [Pd₂(dmba)₂(NO₃)₂(μ-bpe)] (5) (bpe=trans-1,2-bis(4-pyridyl)ethylene; dmba=N,N-dimethylbenzylamine) are described. The thermal stability of [Pd₂(dmba)₂X₂(μ-bpe)] complexes varies in the sequence 1>4>3>2>5. The final residues of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction.     

Darstellung und spektroskopische Charakterisierung der reinen Bindungsisomeren [OsCl5(NCS)]2− und [OsCl5(SCN)]2−

Preparation and Spectroscopic Characterization of the Pure Bondisomers [OsCl₅(NCS)]^2? and [OsCl₅(SCN)]^2? The oxidation of [OsCl₅I]^2? with (SCN)₂ in CH₂Cl₂ yields the bondisomers [OsCl₅(NCS)]^2? and [OsCl₅(SCN)]^2?, which are isolated as pure compounds by ion exchange chromatography on DEAE-Cellulose. Only the salts of the N-isomer show significant shifts in the vibrational and electronic spectra caused by polarization of the terminal S depending on the size of the cations and the polarity of the solvents. In the IR and Raman spectra ν_CN(S), ν_CS(N) and δ_NCS are found at higher wave numbers than ν_CN(N), ν_CS(S) and δ_SCN. In the optical spectrum of the red [OsCl₅(SCN)]^2? the charge-transfer S→Os is nearly constant at 538 nm, but the N→Os transition of the yellow to violet coloured N-isomer shifts from 480 nm in organic solvents or in presence of large alkylammonium cations to 516 nm in aqueous solution and to 544 nm in the solid Cs-salt. The optical electronegativities are calculated to χ_opt(–SCN) = 2.6 and χ_opt(–NCS) = 2.6–2.8. According to spinorbit coupling and to lowered symmetry (C_4v) the splitted intraconfigurational transitions are observed at 10 K as weak peaks in the regions 600, 1000 and 2000 nm. The O? O transitions are calculated from the vibrational fine structure. The lowest level of both isomers is confirmed by peaks in the electronic raman spectra. With the parameters ζ(Os^IV) = 3200 cm^?1 and B(? SCN) = 316 cm^?1 or B(? NCS) = 288 cm^?1 there is a good fit of calculated and experimental data, resulting in the nephelauxetic series: F^? > CI^? > SCN^? > Br^? > NCS^? > I^?.     

Two novel procedures of preparation for [Tc(CO)<Subscript>2</Subscript>(NO)]<Superscript>2+</Superscript>labeled by EHIDA and its biodistribution

To develop potential new Tc radiopharmaceuticals, a novel compound [^99mTc(CO)₂(NO)(EHIDA)]⁰ (EHIDA: 2,6-diethylphenylcarbamoylmethyliminodiacetic acid) has been prepared by reacting [^99mTc(CO)₃)(EHIDA)]⁻ with NOBF₄ both in water and acetonitrile. The conversion of [^99mTc(CO)₃)(EHIDA)]⁻ to [^99mTc(CO)₂(NO)(EHIDA)]⁰ was supported by TLC, HPLC and eletrophoresis. The radiochemical purity (more than 99%) was proved by TLC and HPLC. The biodistribution in mice demonstrated that [Tc(CO)₂(NO)(EHIDA)]⁰ showed higher uptake in blood, kidney and lung (15 min, blood: 19.24±2.95; kidney: 13.61±3.49; lung: 10.81±1.09.) but a lower uptake in liver (15 min, 5.73±0.74). The slower clearances (120 min, blood: 12.75±1.34; kidney: 13.61±3.49) from blood and kidney were also found. This research describes two methods for the conversion of [^99mTc(CO)₃]⁺ into [^99mTc(CO)₂)(NO)]²⁺ by using NOBF₄ as the source of NO⁺ both in organic solvent and water. The latter method offers the possibility to introduce the NO-group in high yield in water.     

Imide and anhydride bridged organoiron dinuclear homo and hetero dichalcogeno carboxylate complexes [CpFe(CO)2ECO(C6H4)CO]2NH and [CpFe(CO)2ECO(C6H4)CO]2O; E = S,Se

Organoiron thio- and seleno-terephthaloyl chloride complexes CpFe(CO)₂ECO(C₆H₄)COCl (E = S and Se) react with NaOH and NaNH₂ to give quantitative yields of the acid Cp(CO)₂ECO(C₆H₄)CO₂H and the amide CpFe(CO)₂ECO(C₆H₄)CONH₂ respectively. These amide and acid derivatives react with the terephthaloyl chloride complexes to give a new series of imide-bridged [CpFe(CO)₂ECO(C₆H₄)CO]₂NH and anhydride-bridged [CpFe(CO)₂ECO(C₆H₄)CO]₂O organoiron dinuclear homo and hetero dichalcogeno terephthalate complexes. The complexes were characterized by elemental analysis, i.r. and ¹H-n.m.r. spectra. This revised version was published online in June 2006 with corrections to the Cover Date.     

Thermoanalytical Study of Linkage Isomerism in Coordination Compounds. Part 7. A DSC and DFT Investigation of Solid‐state Linkage Isomerization in Bis(thiocyanato)‐bipyridineplatinum(II) Complex

The linkage isomerization of [Pt(SCN)₂(bipy)] complex in solid‐state was investigated by differential scanning calorimetry (DSC) at diverse heating rates. The conversion of the bis‐thiocyanato isomer (–SCN)₂ to the bis‐isothiocyanato isomer (–NCS)₂ was accompanied by the appearance of an exothermic peak. However, no DSC peak was obtained for isomerization of the (–NCS)₂. The results imply that the (–SCN)₂ isomer is metastable which can convert to the stable isomer (–NCS)₂ at elevated temperatures. Assuming a two‐stage irreversible isomerization, the enthalpy changes of the first stage ΔH _SCN¹ and also second stage ΔH _SCN² isomerization were obtained (–2.99 ± 0.44 and –2.81 ± 0.45 kJ · mol^–1, respectively) using the mathematical resolution of the observed DSC peaks. The thermokinetic parameters of this conversion were determined using Kissinger method. The activation energy values for the first and second stages of isomerization are evaluated, 101.78 ± 7.58 and 106.26 ± 5.87 kJ · mol^–1, respectively. The low values of the activation enthalpy, ΔH ^? and the high negative activation entropy ΔS ^?, obtained by Eyring equation, supported an associative mechanism. A DFT study was employed to detect the electronic structures and the thermodynamic stabilities of the three linkage isomers and the transition states.     

The Electronic Ground State of [Fe(CO)3(NO)]−: A Spectroscopic and Theoretical Study

During the past 10 years iron‐catalyzed reactions have become established in the field of organic synthesis. For example, the complex anion [Fe(CO)₃(NO)]^?, which was originally described by Hogsed and Hieber, shows catalytic activity in various organic reactions. This anion is commonly regarded as being isoelectronic with [Fe(CO)₄]^2?, which, however, shows poor catalytic activity. The spectroscopic and quantum chemical investigations presented herein reveal that the complex ferrate [Fe(CO)₃(NO)]^? cannot be regarded as a Fe^?II species, but rather is predominantly a Fe⁰ species, in which the metal is covalently bonded to NO^? by two π‐bonds. A metal–N σ‐bond is not observed.     

Synthesis and cleavage reactions of thiocarbonyl-bridged Cp2Fe2(CO)3CS,and preparation of the carbene complexes CpFe(CO)C(N2C2H6)SnPh3 and [CpFe(CO)2C(OMe)2]PF6

The thiocarbonyl-bridged complex Cp₂Fe₂(CO)₃CS is obtained by the reaction of CpFe(CO)₂^? and (PhO)₂CS in THF. Infrared and NMR spectra show that the compound exists in solution in interconverting cis and trans forms, but that the isomerization occurs more slowly than for the carbonyl analog [CpFe(CO)₂]₂. Most reagents which cleave [CpFe(CO)₂]₂, such as Br₂, HgCl₂, and O₂/HBF₄, do not give simple cleavage reactions with Cp₂Fe₂(CO)₃CS. Reductive cleavage of Cp₂Fe₂(CO)₃CS with Na(Hg) gives the thiocarbonyl anion CpFe(CO)(CS)^?, which reacts with Ph₃SnCl to form CpFe(CO)(CS)SnPh₃. Methylamine reacts with CpFe(CO)(CS)SnPh₃ to give CpFe(CO)(CNMe)SnPh₃, while ethylenediamine gives the carbene complexes CpFe(CO)C(N₂C₂H₆)SnPh₃. The preparation of another new carbene complex, [CpFe(CO)₂C(OMe)₂]PF₆, is also described.     

Iron(II) complexes [Fe(DfgH)<Subscript>2</Subscript>(3-CONH<Subscript>2</Subscript>-Py)<Subscript>2</Subscript>] and [Fe(DfgH)<Subscript>2</Subscript>(4-COOC<Subscript>2</Subscript>H<Subscript>5</Subscript>-Py)<Subscript>2</Subscript>]: Synthesis and structures

The complexes [Fe(DfgH)₂(3-CONH₂-Py)₂] (I) and [Fe(DfgH)₂(4-COOC₂H₅-Py)₂] (II), where DfgH₂ is α-benzyl dioxime, were obtained and examined by X-ray diffraction analysis. The equatorial planes of the coordination octahedra of the metal ions consist of two monodeprotonated α-benzyl dioxime residues united through intramolecular hydrogen bonds O-H…O into a pseudomacrocyclic system. The neutral molecules 3-CONH₂-Py and 4-COOC₂H₅-Py are coordinated to the Fe²⁺ ion through the N atom of the heterocycle. Structure I is layered and structure II is molecular. Intermolecular interactions N-H…O are responsible for the formation of layers in crystal structure I.     

Reactivity modes of bridged bimetallic [(η5-C5H5)Fe(CO)]2-μ-dppe with electrophiles. Preparation and reactions of bimetallic hydride complexes

The complex [(η⁵-C₅H₅)Fe(CO)]₂-μ-dppe (dppe = ethane-1,2-bisdiphenylphosphide) (I) reacts with electrophiles through a η-CO and forms Lewis acid O-Adducts with alkylating reagents (giving cationic μ₂-alkoxycarbyne compounds) or with alkulaluminum compounds. Treatment of I with acid affords a stable μ₂-hydride salt (IV), [CpFe(CO)]₂(μ₂-dppe)⁺, which serves as an intermediate in the stepwise hydrogenation (reversibly) of I to a bridged bimetallic dihydride, [CpFe(CO)H]₂-μ₂-dppe. This dihydride serves as a hydride donor, regenerating IV, towards Ph₃c⁺ or CpFe(CO)₂(η²-CH₂CH₂)⁺ hydride acceptors. The necessity of the μ₂-dppe as a “mechanical linkage” in facilitating some bimetalic reactions is also established.     

[Fe2(μsb‐CO)(CO)3(NO)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)]: Synthese,Kristallstruktur und Koordinationsisomerie

[Fe₂(μ_sb‐CO)(CO)₃(NO)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)]: Synthesis, X‐ray Crystal Structure and Isomerization Na[Fe₂(μ‐CO)(CO)₆(μ‐P^tBu₂)] ( 1 ) reacts with [NO][BF₄] at —60 °C in THF to the nitrosyl complex [Fe₂(CO)₆(NO)(μ‐P^tBu₂)] ( 2 ). The subsequent reaction of 2 with phosphanes (L) under mild conditions affords the complexes [Fe₂(CO)₅(NO)L(μ‐P^tBu₂)], L = PPh₃, ( 3a ); η‐dppm (dppm = Ph₂PCH₂PPh₂), ( 3b ). In this case the phosphane substitutes one carbonyl ligand at the iron tetracarbonyl fragment in 2 , which was confirmed by the X‐ray crystal structure analysis of 3a . In solution 3b loses one CO ligand very easily to give dppm as bridging ligand on the Fe‐Fe bond. The thus formed compound [Fe₂(CO)₄(NO)(μ‐P^tBu₂)(μ‐dppm)] ( 4 ) occurs in solution in different solvents and over a wide temperature range as a mixture of the two isomers [Fe₂(μ_sb‐CO)(CO)₃(NO)(μ‐P^tBu₂)(μ‐dppm)] ( 4a ) and [Fe₂(CO)₄(μ‐NO)(μ‐P^tBu₂)(μ‐dppm)] ( 4b ). 4a was unambiguously characterized by single‐crystal X‐ray structure analysis while 4b was confirmed both by NMR investigations in solution as well as by means of DFT calculations. Furthermore, the spontaneous reaction of [Fe₂(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 5 ) with NO at —60 °C in toluene yields a complicated mixture of products containing [Fe₂(μ‐CO)(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 6 ) as main product beside the isomers 4a and 4b occuring in very low yields.     

The inverse sandwich complex [(K(18-crown-6))2Cp][CpFe(CO)2]--unpredictable redox reactions of [CpFe(CO)2]I with the silanides Na[SiRtBu2] (R = Me, tBu) and the isoelectronic phosphanyl borohydride K[PtBu2BH3

The dimeric iron carbonyl [CpFe(CO)(2)](2) and the iodosilanes tBu(2)RSiI were obtained from the reaction of [CpFe(CO)(2)]I with the silanides Na[SiRtBu(2)] (R = Me, tBu) in THF. By the reactions of [CpFe(CO)(2)]I and Na[SiRtBu(2)] (R = Me, tBu) the disilanes tBu(2)RSiSiRtBu(2) (R = Me, tBu) were additionally formed using more than one equivalent of the silanide. In this context it should be noted that reduction of [CpFe(CO)(2)](2) with Na[SitBu(3)] gives the disilanes tBu(3)SiSitBu(3) along with the sodium ferrate [(Na(18-crown-6))(2)Cp][CpFe(CO)(2)]. The potassium analogue [(K(18-crown-6))(2)Cp][CpFe(CO)(2)] (orthorhombic, space group Pmc2(1)), however, could be isolated as a minor product from the reaction of [CpFe(CO)(2)]I with [K(18-crown-6)][PtBu(2)BH(3)]. The reaction of [CpFe(CO)(2)](2) with the potassium benzophenone ketyl radical and subsequent treatment with 18-crown-6 yielded the ferrate [K(18-crown-6)][CpFe(CO)(2)] in THF at room temperature. The crown ether complex [K(18-crown-6)][CpFe(CO)(2)] was analyzed using X-ray crystallography (orthorhombic, space group Pna2(1)) and its thermal behaviour was investigated.     

Density Functional Theory and Low-Temperature Matrix Investigations of CO-Loss Photochemistry from [(C<Subscript>5</Subscript>R<Subscript>5</Subscript>)Ru(CO)<Subscript>2</Subscript>]<Subscript>2</Subscript> (R = H,Me) Complexes

The photochemical CO-loss products of the diruthenium complexes [CpRu(CO) ₂]₂ (5; Cp = ⁵-C₅H₅), [Cp*Ru(CO)₂]₂ (5*; Cp* = ⁵-C₅(CH₃)₅) and CpCp*[Ru(CO)₂]₂ (5) have been studied experimentally in low-temperature (96 K) matrices in 3-methylpentane by using IR spectroscopy. It is proposed that all three complexes undergo single-CO-loss chemistry but that the products have different structures. The single-CO-loss product from 5 is proposed to have one bridging and two terminal carbonyl ligands, whereas 5* and 5 generate triply bridged CO-loss products similar to that observed from [CpFe(CO)₂]₂ and [Cp*Fe(CO)₂]₂. Double-CO-loss from 5* and 5* 9 is also apparently observed. Relativistic DFT calculations have been carried out on various isomers of the starting materials and on potential CO-loss products from 5. The calculations suggest that the triply bridged product Cp₂Ru₂(-CO)₃ (6) might have a singlet ground state in contrast to the corresponding diiron complex Cp₂Fe₂(-CO)₃ (3), which has a triplet ground state.     

Synthesis and Characterization of Terminal [Re(XCO)(CO)2(triphos)] (X=N,P): Isocyanate versus Phosphaethynolate Complexes

The terminal rhenium(I) phosphaethynolate complex [Re(PCO)(CO)₂(triphos)] has been prepared in a salt metathesis reaction from Na(OCP) and [Re(OTf)(CO)₂(triphos)]. The analogous isocyanato complex [Re(NCO)(CO)₂(triphos)] has been likewise prepared for comparison. The structure of both complexes was elucidated by X‐ray diffraction studies. While the isocyanato complex is linear, the phosphaethynolate complex is strongly bent around the pnictogen center. Computations including natural bond orbital (NBO) theory, natural resonance theory (NRT), and natural population analysis (NPA) indicate that the isocyanato complex can be viewed as a classic Werner‐type complex, that is, with an electrostatic interaction between the Re^I and the NCO group. The phosphaethynolate complex [Re(P?C?O)(CO)₂(triphos)] is best described as a metallaphosphaketene with a Re^I–phosphorus bond of highly covalent character.     

Two novel four-coordinated zinc(II) complexes [Zn(dmatrz)<Subscript>2</Subscript>Cl<Subscript>2</Subscript>] and [Zn(dmatrz)<Subscript>2</Subscript>(SCN)<Subscript>2</Subscript>] exhibiting strong blue fluorescent properties

Two novel complexes, [Zn(dmatrz)₂]Cl₂ (1) and [Zn(dmatrz)₂(SCN)₂] (2), have been prepared and characterized by X-ray crystallography, absorption and luminescence spectrometries (dmatrz=3,5-dimethy-4-amino-1,2,4-triazole). The coordination environment of the zinc(II) ions in (1) and (2) has a distorted tetrahedral geometry completed via two independent nitrogen atoms of two triazole ligands and two anions, respectively. Both (1) and (2) show strong blue luminescence properties. Furthermore, (1) displays stronger blue photoluminescence than (2) as the result of different anions (Cl^- and SCN^-) coordinated to the zinc(II) ions.