(p, ρ, T) properties, and apparent molar volumes V? of ZnBr2 in methanol at T = (298.15 to 398.15) K and pressures up to p = 40 MPa

The (p, ρ, T) properties of pure methanol, the (p, ρ, T) properties and apparent molar volumes V_? of ZnBr₂ in methanol at T = (298.15 to 398.15) K and pressures up to p = 40 MPa are reported, and apparent molar volumes have been evaluated. The experimental (p, ρ, T, m) values were described by an equation of state. For the solutions the experiments were carried out at molalities m = (0.05772, 0.37852, 0.71585 and 1.95061) mol · kg⁻¹ of zinc bromide.     

The investigation of the (p,ρ,T) and (ps,ρs,Ts) properties of {(1−x)CH3OH + xLiBr} for the application in absorption refrigeration machines and heat pumps

The (p,ρ,T) and (p_s,ρ_s,T_s) properties of {(1−x)CH₃OH + xLiBr} over a wide range of state parameters are reported for the first time. The experiments were carried out in a constant volume piezometer over a temperature range from 298.15 K to 398.15 K, at 0.08421, 0.13617, 0.19692, 0.23133 and 0.26891 mole fractions and from atmospheric pressure up to 60 MPa. The experimental uncertainties are ΔT=±3 mK for temperature, Δp=±5·10⁻² MPa for high pressure and Δp=±5·10⁻⁴ MPa for atmospheric pressure, Δρ=±3·10⁻² kg · m⁻³ for density. An equation of state was derived for correlation of the experimental data of the solutions.     

Apparent molar volumes and apparent molar heat capacities of aqueous N-acetyl-d-glucosamine at temperatures from 278.15 K to 368.15 K and of aqueous N-methylacetamide at temperatures from 278.15 K to 393.15 K at the pressure 0.35 MPa

We determined apparent molar volumes V_? from densities measured with a vibrating-tube densimeter at 278.15 ? (T/K) ? 368.15 and apparent molar heat capacities C_p,? with a twin fixed-cell, differential, temperature-scanning calorimeter at 278.15 ? (T/K) ? 363.15 for aqueous solutions of N-acetyl-d-glucosamine at m from (0.01 to 1.0) mol · kg⁻¹ and at p = 0.35 MPa. We also determined V_? at 278.15 ? (T/K) ? 368.15 and C_p,? at 278.15 ? (T/K) ? 393.15 for aqueous solutions of N-methylacetamide at m from (0.015 to 1.0) mol · kg⁻¹ and at p = 0.35 MPa. Empirical functions of m and T for each compound were fitted to our results, which are then compared to those for N,N-dimethylacetamide. Estimated values of Δ_rV_m(m, T) and Δ_rC_p,m(m, T) for formation of aqueous N-acetyl-d-glucosamine from aqueous d-glucose and aqueous acetamide are calculated and discussed.     

Synthesis, characterization and Schlenk equilibrium studies of methylmagnesium compounds with O- and N-donor ligands - the unexpected behavior of [MgMeBr(pmdta)] (pmdta = N,N,N′,N″,N″-pentamethyldiethylenetriamine)

MgMe₂ (1) was found to react with 1,4-diazabicyclo[2.2.2]octane (dabco) in tetrahydrofuran (thf) yielding a binuclear complex [{MgMe₂(thf)}₂(μ-dabco)] (2). Furthermore, from reactions of MgMeBr with diglyme (diethylene glycol dimethyl ether), NEt₃, and tmeda (N,N,N′,N′-tetramethylethylenediamine) in etheral solvents compounds MgMeBr(L), (L = diglyme (5); NEt₃ (6); tmeda (7)) were obtained as highly air- and moisture-sensitive white powders. From a thf solution of 7 crystals of [MgMeBr(thf)(tmeda)] (8) were obtained. Reactions of MgMeBr with pmdta (N,N,N′,N″,N″-pentamethyldiethylenetriamine) in thf resulted in formation of [MgMeBr(pmdta)] (9) in nearly quantitative yield. On the other hand, the same reaction in diethyl ether gave MgMeBr(pmdta) · MgBr₂(pmdta) (10) and [{MgMe₂(pmdta)}₇{MgMeBr(pmdta)}] (11) in 24% and 2% yield, respectively, as well as [MgMe₂(pmdta)] (12) as colorless needle-like crystals in about 26% yield. The synthesized methylmagnesium compounds were characterized by microanalysis and ¹H and ¹³C NMR spectroscopy. The coordination-induced shifts of the ¹H and ¹³C nuclei of the ligands are small; the largest ones were found in the tmeda and pmdta complexes. Single-crystal X-ray diffraction analyses revealed in 2 a tetrahedral environment of the Mg atoms with a bridging dabco ligand and in 8 a trigonal-bipyramidal coordination of the Mg atom. The single-crystal X-ray diffraction analyses of [MgMe₂(pmdta)] (12) and [MgBr₂(pmdta)] (13) showed them to be monomeric with five-coordinate Mg atoms. The square-pyramidal coordination polyhedra are built up of three N and two C atoms in 12 and three N and two Br atoms in 13. The apical positions are occupied by methyl and bromo ligands, respectively. Temperature-dependent ¹H NMR spectroscopic measurements (from 27 to −80 °C) of methylmagnesium bromide complexes MgMeBr(L) (L = thf (4); diglyme (5); NEt₃ (6); tmeda (7)) in thf-d₈ solutions indicated that the deeper the temperature the more the Schlenk equilibria are shifted to the dimethylmagnesium/dibromomagnesium species. Furthermore, at −80 °C the dimethylmagnesium compounds are predominant in the solutions of Grignard compounds 4-6 whereas in the case of the tmeda complex7 the equilibrium constant was roughly estimated to be 0.25. In contrast, [MgMeBr(pmdta)] (9) in thf-d₈ revealed no dismutation into [MgMe₂(pmdta)] (12) and [MgBr₂(pmdta)] (13) even up to −100 °C. In accordance with this unexpected behavior, 1:1 mixtures of 12 and 13 were found to react in thf at room temperature yielding quantitatively the corresponding Grignard compound 9. Moreover, the structures of [MgMeBr(pmdta)] (9c), [MgMe₂(pmdta)] (12c), and [MgBr₂(pmdta)] (13c) were calculated on the DFT level of theory. The calculated structures 12c and 13c are in a good agreement with the experimentally observed structures 12 and 13. The equilibrium constant of the Schlenk equilibrium (2 9c ? 12c + 13c) was calculated to be K_gas = 2.0 × 10⁻³ (298 K) in the gas phase. Considering the solvent effects of both thf and diethyl ether using a polarized continuum model (PCM) the corresponding equilibrium constants were calculated to be K_thf = 1.2 × 10⁻³ and K_ether = 3.2 × 10⁻³ (298 K), respectively.     

Measurements of the isochoric heat capacity,the critical point (TC, ρC) and vapor–liquid coexistence curve (TS, ρS) of high-purity toluene near the critical point

Isochoric heat capacities (C_V, V, T), phase boundary properties (T_S, ρ_S) and the critical (T_C, ρ_C) parameters for high-purity (0.9999+ mole fraction) toluene have been measured with a high temperature, high pressure, nearly constant volume adiabatic calorimeter and quasi-static thermogram technique. Measurements were made at three selected liquid and vapor isochores 777.8, 555.25, and 214.64 kg m⁻³ in the temperature range from 379 to 591 K. For five near-critical isochores 268.68, 281.68, 296.62, 301.52, and 318.28 kg m⁻³, the measurements were made in the immediate vicinity of the coexistence curve in order to accurately determine the phase transition temperatures (T_S, ρ_S) (shape of the coexistence curve near the critical point) and the critical parameters (T_C, ρ_C). The total combined uncertainty of heat capacity, density, and temperature measurements were estimated to be less than 2%, 0.06%, and 15 mK, respectively. The uncertainties reported in this paper are expanded uncertainties at the 95% confidence level with a coverage factor of k = 2. The uncertainty of the phase transition and the critical temperature value was 0.02 K. The Krichevskii parameter for some toluene-containing binary mixtures was calculated. The derived values of the Krichevskii parameter were used to estimate the effect of dilute impurities on the critical parameters of toluene. The measured values of saturated density near the critical point were interpreted in terms of the “complete scaling” theory in order to study singularity behavior of the coexistence curve diameter. The measured isochoric heat capacities and saturated densities were compared with the data reported by other authors and values calculated from an equation of state and other correlations.     

Effect of phase behavior, density, and isothermal compressibility on the constant-volume heat capacity of ethane + n-pentane mixed fluids in different phase regions

The phase behavior, density, and constant-volume molar heat capacity (C_v,m) of ethane + n-pentane binary mixtures have been measured in the supercritical region and subcritical region at T=309.45 K. In addition, the isothermal compressibility (κ_T) has been calculated using the density data determined. For a mixed fluid with a composition close to the critical composition, C_v,m and κ_T increase sharply as the pressure approaches the critical point (CP), the dew point (DP), or the bubble point (BP). However, C_v,m is not sensitive to pressure in the entire pressure range if the composition of the mixed fluid is far from the critical composition. To tune the properties of the binary mixtures effectively by pressure, both the composition and the pressure should be close to the critical point of the mixture. The intermolecular interactions in the mixture are also discussed on the basis of the experimental results.     

Thermodynamic study of the n-octane-1-pentanol-sodium dodecyl sulfate solutions in water

The thermodynamic properties, PVTx (T_S, P_S, ρ_S), (∂P/∂T)_VX, and C_VVTx, of three microemulsions (water + n-octane + sodium dodecylsulfate + 1-pentanol) with composition of solution-1: 0.0777 (H₂O):0.6997 (n-C₈H₁₈):0.0777 (SDS):0.1449 (1-C₅H₁₁OH) mass fraction; solution-2: 0.6220 (H₂O):0.1555 (n-C₈H₁₈):0.0777 (SDS):0.1448 (1-C₅H₁₁OH) mass fraction; and solution-3: 0.2720 (H₂O):0.5054 (n-C₈H₁₈):0.0777 (SDS):0.1449 (1-C₅H₁₁OH) mass fraction were measured. Sodium dodecylsulfate (SDS) was used as an ionic surfactant, 1-pentanol used as stabilizer (cosurfactant), and n-octane as oil component in aqueous solution. A high-temperature, high-pressure, adiabatic, and nearly constant-volume calorimeter supplemented by quasi-static thermogram technique was used for the measurements. Measurements were made at eight densities (isochores) between 475.87 and 919.03 kg m⁻³. The range of temperature was from 275 to 536 K and pressure range was up to 138 bar. Uncertainty of the pressure, density, derivative (∂P/∂T)_VX, and heat capacity measurements are estimated to be 0.25%, 0.02%, 0.12-1.5%, and 2.5%, respectively. Temperatures at liquid-gas phase transition curve, T_S(ρ), for each measured densities (isochores) were determined using a quasi-static thermogram technique. The uncertainty of the phase transition temperature measurements is about ±0.02 K. The effect of temperature, density, and concentration on the heat capacity of the microemulsions is discussed. Along the isochore of 438.40 kg m⁻³ at temperatures above 525.44 K for the first solution the precipitation of the solid phase (SDS) was found.     

Vapour pressure and excess Gibbs free energy of binary mixtures of hydrogen sulphide with ethane, propane, and n-butane at temperature of 182.33 K

The vapour pressure of binary mixtures of hydrogen sulphide with ethane, propane, and n-butane was measured at T = 182.33 K covering most of the composition range. The excess Gibbs free energy of these mixtures has been derived from the measurements made. For the equimolar mixtures for (H₂S + C₂H₆), (820.1 ± 2.4) J · mol⁻¹ for (H₂S + C₃H₈), and (818.6 ± 0.9) J · mol⁻¹ for (H₂S + n-C₄H₁₀). The binary mixtures of H₂S with ethane and with propane exhibit azeotropes, but that with n-butane does not.     

Critical parameters for propane determined by the image analysis

The (p, ρ, T) measurements and visual observations of the meniscus for propane were carried out carefully in the critical region over the range of temperatures: ?60 mK ? (T ? T_c) ?  40 mK and of densities: ?4 kg · m^?3 ? (ρ ? ρ_c) ? 6 kg · m^?3 by a metal-bellows volumometer with an optical cell. Vapour pressures were also measured at T = (320.000, 343.132, 369.000, and 369.625) K. The critical point of T_c, ρ_c, and p_c was determined by the image analysis of the critical opalescence. Comparisons of the critical parameters with values given in the literature are presented.     

Theoretical study of the thermochemistry and the kinetics of the SFxCl (x = 0-5) series

A systematic thermodynamic and kinetic study of the entire SF_xCl (x = 0-5) series has been carried out. High-level quantum chemical composite methods have been employed to derive enthalpy of formation values from calculated atomization and isodesmic energies. The resulting values for the SCl, SFCl, SF₂Cl(C₁), SF₃Cl(C_s), SF₄Cl(C_s) and SF₅Cl molecules are 28.0, −36.0, −64.2, −134.3, −158.2 and −237.1 kcal mol⁻¹. A comparison with previous experimental and theoretical values is presented. Statistical adiabatic channel model/classical trajectory, SACM/CT, calculations of selected complex-forming and recombination reactions of F and Cl atoms with radicals of the series have been performed between 200 and 500 K. The reported rate coefficients span over the normal range of about 6 × 10⁻¹² and 5 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ expected for this type of barrierless reactions.     

Thermodynamic properties of hydrated sodium l-threonate Na(C4H7O5)·H2O(s)

Low-temperature heat capacities of the compound Na(C₄H₇O₅)·H₂O(s) have been measured with an automated adiabatic calorimeter. A solid-solid phase transition and dehydration occur at 290-318 K and 367-373 K, respectively. The enthalpy and entropy of the solid-solid transition are Δ_transH_m = (5.75 ± 0.01) kJ mol⁻¹ and Δ_transS_m = (18.47 ± 0.02) J K⁻¹ mol⁻¹. The enthalpy and entropy of the dehydration are Δ_dH_m = (15.35 ± 0.03) kJ mol⁻¹ and Δ_dS_m = (41.35 ± 0.08) J K⁻¹ mol⁻¹. Experimental values of heat capacities for the solids (I and II) and the solid-liquid mixture (III) have been fitted to polynomial equations.     

Thermodynamics of complexation of aqueous 18-crown-6 with potassium ion: apparent molar volumes and apparent molar heat capacities of aqueous 18-crown-6 and of the (18-crown-6 + potassium chloride) complex at temperatures (278.15 to 393.15) K, at molalities (0.02 to 0.3) mol · kg, and at the pressure 0.35 MPa

We have measured the densities at temperatures T = (278.15 to 363.15) K and heat capacities at T = (278.15 to 393.15) K of aqueous solutions of 18-crown-6 and of (18-crown-6 + KCl) at molalities m = (0.02 to 0.3) mol · kg⁻¹ and at the pressure 0.35 MPa. We have calculated apparent molar volumes V_? and apparent molar heat capacities C_p,? for 18-crown-6(aq), and we have applied Young’s Rule and have accounted for chemical speciation and relaxation effects to resolve V_? and C_p,? for the (18-crown-6: K⁺,Cl⁻)(aq) complex in the mixture. We have also calculated estimates of the change in volume Δ_rV_m, the change in heat capacity Δ_rC_p,m, the change in enthalpy Δ_rH_m, and the equilibrium quotient log Q for formation of the complex at T = (278.15 to 393.15) K and m = (0 to 0.3) mol · kg⁻¹.     

Synthesis and properties of novel 5-(cyclohepta-2′,4′,6′-trienylidene)pyrimidine-2(1H),4(3H),6(5H)-triones: methodology for synthesizing cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborates

Novel condensation reaction of tropone with N-substituted and N,N′-disubstitued barbituric acids in Ac₂O afforded 5-(cyclohepta-2′,4′,6′-trienylidene)pyrimidine-2(1H),4(3H),6(5H)-trione derivatives (8a-f) in moderate to good yields. The ¹³C NMR spectral study of 8a-f revealed that the contribution of zwitterionic resonance structures is less important as compared with that of 8,8-dicyanoheptafulvene. The rotational barriers (ΔG^‡) around the exocyclic double bond of mono-substituted derivatives 8a-c were obtained to be 14.51-15.03 kcal mol⁻¹ by the variable temperature ¹H NMR measurements. The electrochemical properties of 8a-f were also studied by CV measurement. Upon treatment with DDQ, 8a-c underwent oxidative cyclization to give two products, 7 and 9-substituted cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborates (11a-c·BF₄⁻ and 12a-c·BF₄⁻) in various ratios, while that of disubstituted derivatives 8d-f afforded 7,9-disubstituted cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborate (11d-f·BF₄⁻) in good yields. Similarly, preparation of known 5-(1′-oxocycloheptatrien-2′-yl)-pyrimidine-2(1H),4(3H),6(5H)-trione derivatives (14a-d) and novel derivatives 14e,f was carried out. Treatment of 14a-c with aq. HBF₄/Ac₂O afforded two kinds of novel products 11a-c·BF₄⁻ and 12a,c·BF₄⁻ in various ratios, respectively, while that of 14d-f afforded 11d-f. The product ratios of 11a-c·BF₄⁻ and 12a-c·BF₄⁻ observed in two kinds of cyclization reactions were rationalized on the basis of MO calculations of model compounds 20a and 21a. The spectroscopic and electrochemical properties of 11a-f·BF₄⁻ and 12a-c·BF₄⁻ were studied, and structural characterization of 11c·BF₄⁻ based on the X-ray crystal analysis and MO calculation was also performed.     

Design of single chain magnets through cyanide-bearing six-coordinate complexes

The design and preparation of stable cyanide-bearing six-coordinate complexes of formula [M^III(L)(CN)_x]^{(x + l − m)−} (M = trivalent transition metal ion and L = polydentate blocking ligand) are summarized here. Their use as ligands towards either fully hydrated metal ions or coordinatively unsaturated preformed species, to afford a wide variety of low-dimensional metal assemblies whose nuclearity, dimensionality and magnetic properties can be tuned, is also reviewed. Special emphasis is put on the appropriate choice of the end-cap ligand L whose denticity determines the number of coordinated cyanide groups in the mononuclear precursors. Among the different new spin topologies obtained through this rational synthetic strategy, ferromagnetically coupled 4,2-ribbon like bimetallic chains which exhibit slow magnetic relaxation and hysteresis effects (chain as magnets) are one of the most appealing and constitute the heart of the present contribution.     

Heat capacity, enthalpy and entropy of bismuth niobate and bismuth tantalate

The heat capacity and the heat content of bismuth niobate BiNbO₄ and bismuth tantalate BiTaO₄ were measured by the relaxation method and Calvet-type heat flux calorimetry. The temperature dependencies of the heat capacities in the form C_pm=128.628+0.03340 T−1991055/T²+136273131/T³ (J K^-1 mol^-1) and 133.594+0.02539 T−2734386/T²+235597393/T³ (J K^-1 mol^-1) were derived for BiNbO₄ and BiTaO₄, respectively, by the least-squares method from the experimental data. Furthermore, the standard molar entropies at 298.15 K S_m(BiNbO₄)=147.86 J K^-1 mol^-1 and S_m(BiTaO₄)=149.11 J K^-1 mol^-1 were assessed from the low temperature heat capacity measurements. To complete a set of thermodynamic data of these mixed oxides an attempt was made to estimate the values of the heat of formation from the constituent binary oxides.     

Crosslinking, thermal properties and relaxation behaviour of polyisoprene under high-pressure

The transient hot-wire method has been used to measure the thermal conductivity κ and heat capacity per unit volume ρc_p of untreated (virgin) and crosslinked cis-1,4-poly(isoprene) (PI) in the temperature range 160-513 K for pressures p up to 0.75 GPa. The results show that the crosslinking rate of the polymer chains becomes significant at ∼513 K on isobaric heating at 0.5 GPa changing PI into an elastomeric state within 4 h without the use of crosslinking agents. The crosslinked PI and untreated PI have about the same κ = 0.145 Wm⁻¹ K⁻¹ and c_p = 1.81 kJ kg⁻¹ K⁻¹ at 295 K and 20 MPa, but different relaxation behaviours. Two relaxation processes, corresponding to the segmental and normal modes, could be observed in both PI and crosslinked PI but these have a larger distribution of relaxation times and become arrested at higher temperatures (∼10 K) in the latter case. The arrest temperature for the segmental relaxation of untreated and crosslinked PI, for a relaxation time of ∼1 s, are described well by the empirical relations: T(p) = 209.4 (1 + 4.02 p)^0.31 and T(p) = 221.3 (1 + 2.33 p)^0.40 (p in GPa and T in K), respectively, which thus also reflects the pressure variations of the glass transition temperatures.     

Tetrazole derivatives and matrices as novel cobalamin coordinating compounds

Cobalamin (Cbl, vitamin B₁₂) consists of two moieties: (i) the corrin ring with the central Co-ion in the oxidation states Co^3+/2+/1+ and (ii) the nucleotide side chain. The lower position of the ring is typically occupied by the nucleotide base (Bzm), whereas the upper surface coordinates exchangeable ligands. We have found that amino-tetrazole can coordinate to H₂O · Cbl (Co³⁺) with K_d = 10⁻⁵-10⁻⁶ M. A specific group (presumably tetrazole, TZ) can be easily created in CNBr-activated Sepharose by treatment with . The prepared matrix (STZ) contained ≈10 mM of the active groups, which bound H₂O · corrinoids with K_d = 10⁻⁵-10⁻⁶ M. Stability of STZ-Cbl bonds gradually increased and reached K_d = 10⁻⁷ M over 10-20 h (20 °C, pH 6-7). This effect can be ascribed to partial displacement of Bzm and coordination of TZ to the lower position. The binding was most efficient at pH 4-7 and low ionic strength, yet, noticeable adsorption took place even at extreme conditions, pH 1-9 and I = 0-2 M. Reduced corrins (Co²⁺) also exhibited high affinity for STZ. The bound ligands could be eluted as H₂O · Cbl (pH 0), HO · Cbl (pH 14) or diCN · Cbl (pH 9-12, CN⁻). The adsorbent is applicable for one-step purification of corrins from a crude extract; separation of aquo- and diaquo-forms; specific capturing of H₂O · Cbl from a mixture containing organo-Cbls or protein-bound Cbl, analysis of peptide-Cbl dissociation kinetics, etc.     

A methodology to define the Cubic Equation of State of a simple fluid

A method to define the Cubic Equation of State (CES) of a simple substance is presented in this work. CES is constructed with only three parameters of the fluid, namely, the critical compressibility Z_c≡P_cv_c/RT_c, the acentric factor ω ≡ − log  (P^(sat)/P_c) − 1 (where P^(sat) is the saturated vapor pressure), and the saturated vapor volume v^(sat) at the temperature T^(sat)/T_c = 0.7 (where T_c is the critical temperature, v_c is the critical volume, and P_c is the critical pressure). The resulting CES is unique for each substance and, in general, it is different from other known CES in the literature.     

Heat-capacity measurements and thermodynamic functions of crystalline adenine; revised thermodynamic properties of aqueous adenine

The standard molar heat capacity C^°_p,m of adenine(cr) has been measured using adiabatic calorimetry over the range 6<(T/K)<310 and the results used to derive thermodynamic functions for adenine(cr) at smoothed temperatures. At T=298.15 K, C^°_p,m=(142.67±0.29) J · K⁻¹ · mol⁻¹ and the third law entropy S^°_m=(145.62±0.29) J · K⁻¹ · mol⁻¹. The standard molar Gibbs free energy of formation Δ_fG^°_m at T=298.15 K for crystalline adenine was calculated, using the standard molar enthalpy of formation for the compound and entropies of the elements from the literature, and found to be Δ_fG^°_m=(301.4±1.0) kJ · mol⁻¹. The results were combined with solution calorimetry and solubility measurements from the literature to yield revised values for the standard molar thermodynamic properties of aqueous adenine at T=298.15 K: Δ_fG^°_m=(313.4±1.0) kJ · mol⁻¹, Δ_fH^°_m=(129.5±1.4) kJ · mol⁻¹, and S_m^°=(217.68±0.44) J · K⁻¹ · mol⁻¹.     

N,N-polymethylene-bisadenine complexes with d metal ions

The reaction of N⁹,N^9′-(tri or tetramethylene)-bisadenines (Ade₂C_x; x = 3 or 4) in HCl 2 M at 50 °C with MCl₂ · 2H₂O [M = Zn(II), Cd(II)] yields outer sphere compounds like the previously described [(H-Ade)₂C₃][ZnCl₄] · H₂O (3) and [(H-Ade)₂C₃]₂[Cd₂Cl₈(H₂O)₂] · 4H₂O (4) for Ade₂C₃ and the new {[(H-Ade)₂C₄][Cd₂Cl₆(H₂O)₂] · 2H₂O}_n (5) for Ade₂C₄. On the other hand, only in case of Zn(II) complexes by changing [HCl] to 0.1 M, the inner sphere compounds [H-(Ade)₂C₃(ZnCl₃)] (6) and [H-(Ade)₂C₄(ZnCl₃)] · 1.5H₂O (7) are obtained. X-ray diffraction study of compound 6, which represents the first inner sphere complex with a N⁹,N^9′-bisadenine, shows a zwitterionic form with one adenine ring protonated at N(1) while the other ring is coordinated via N(7) to a ZnCl₃ moiety as in other alkyl-adenine derivatives. In addition, with Ade₂C₄, is also possible to obtain another inner sphere complex: [(H-Ade)₂C₄(ZnCl₃)₂] · 3H₂O (8).