Clustering dynamics of the metal-benzene sandwich complex: the role of microscopic structure of the solute in the bis(eta6-benzene)chromium .Arn Clusters (n = 1-15)

Ar clustering dynamics around the metal-benzene sandwich complex, bis(eta (6)-benzene)chromium: Cr(Bz) 2, is found to occur in two distinct regimes. The shift of the ionization potential (IP) upon the addition of Ar is measured to be 151 cm (-1), and it is constant until the number of Ar solvents ( n) becomes 6. The IP shift per Ar is found to be suddenly decreased to 82 cm (-1) for the clusters of n = 7-12. The cluster distribution indicates that the n = 6 cluster is most populated in the molecular beam. These experimental findings with the aid of ab initio calculation indicate that the first six Ar solvent molecules are attached to top and bottom of Cr(Bz) 2 to give the robust structure for the Cr(Bz) 2-Ar 6 cluster whereas the next six Ar molecules are gathered on the side of the solute core to give the highly symmetric structure of the Cr(Bz) 2-Ar 12 cluster.     

Size- and shape-dependent polarizabilities of sandwich and rice-ball Co(n)Bz(m) clusters from density functional theory

The dipole polarizabilities of Co(n)Bz(m), (n, m = 1-4, m = n, n + 1) clusters are studied by means of an all-electron gradient-corrected density functional theory and finite field method. The dipole moments are relatively large for most of the clusters, implying their asymmetric structures. The total polarizability increases rapidly as cluster size, whereas the average polarizability shows "odd-even" oscillation with relatively large values at (n, n + 1). The polarizabilities exhibit clear shape-dependent variation, and the sandwich structures have systematically larger polarizability and anisotropy than the rice-ball isomers. The dipole polarizabilities are further analyzed in terms of the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap, ionization potential, and electron delocalization volume. We conclude that the polarizability variations are determined by the interplay between the geometrical and electronic properties of the clusters.     

Structural, electronic, and magnetic properties of Con(benzene)m complexes

The structural, electronic, and magnetic properties of cobalt-benzene complexes (Co(n)Bz(m), n, m = 1-4, m = n, n + 1) have been explored within the framework of an all electron gradient-corrected density functional theory. Sandwich conformations are energetically preferred for the smallest series of n, m = 1-2, rice-ball structures are for larger sizes with n > or = 3, and both motifs coexist for Co(2)Bz(3). The rice-ball clusters of (3, 3) and (4, 4) are more stable than (3, 4) having a relative large binding energy and HOMO-LUMO gap whereas smaller sandwich clusters have highly kinetic stability at (n, n + 1). The computed ionization potentials and magnetic moments of Co(n)Bz(m) are in good agreement with the measured values overall; the present results suggest that the measured moments are averages reflecting mixtures of a few nearly isoenergetic isomers having different spin states. The magnetism of the complexes mainly comes from Co atoms with a Bz molecule only possessing very small moments. Ferromagnetic ordering is energetically preferred for smaller complexes with n = 1-3 whereas antiferromagnetic ordering is favored for (4, 4). The relatively smaller moments of Con clusters in a Bz matrix indicate that Bz molecules play an attenuation role to the magnetism of the complexes.     

Cs*He(n) exciplexes in solid 4He

We present a theoretical and experimental study of the laser-induced formation process and of the emission spectra of Cs*He(n) exciplexes in the hcp and bcc phases of solid helium. Two different exciplex molecules are detected: a linear triatomic Cs*He2, which can exist in two electronic states: APi(1/2) and BPi(3/2), and a larger complex, where six or seven He atoms form a ring around a single cesium atom in the 6P(1/2) state. A theoretical model is presented, which allows the interpretation of the experimentally observed spectra.     

Experimental and theoretical evidence for U(C6H6) and Th(C6H6) complexes

The vibrational spectra of UBz and ThBz have been measured in solid argon. Complementary quantum chemical calculations have allowed the assignments of the vibrational spectra. According to the calculations, AcBz are stable molecules, as well as other species like BzAcBz and BzAc2Bz. Experimentally, there is no evidence for the sandwich compounds BzAcBz and BzAc2Bz due to the limitations in the reagent concentrations.     

Geometry and electronic structure of Vn(Bz)m complexes

First-principles calculations based on the generalized gradient approximation to the density functional theory are performed to explore the global geometries, ground-state spin multiplicities, relative stabilities, and energetics of neutral and anionic V(n)(Bz)(m) (n=1-3, m=1-4, with n相似文献   

Electronic properties of hydrogen-bonded complexes of benzene(HCN)(1-4): comparison with benzene(H2O)(1-4)

The electronic properties, specifically, the dipole and quadrupole moments and the ionization energies of benzene (Bz) and hydrogen cyanide (HCN), and the respective binding energies, of complexes of Bz(HCN)(1-4), have been studied through MP2 and OVGF calculations. The results are compared with the properties of benzene-water complexes, Bz(H(2)O)(1-4), with the purpose of analyzing the electronic properties of microsolvated benzene, with respect to the strength of the CH/π and OH/π hydrogen-bond (H-bond) interactions. The linear HCN chains have the singular ability to interact with the aromatic ring, preserving the symmetry of the latter. A blue shift of the first vertical ionization energies (IEs) of benzene is observed for the linear Bz(HCN)(1-4) clusters, which increases with the length of the chain. NBO analysis indicates that the increase of the IE with the number of HCN molecules is related to a strengthening of the CH/π H-bond, driven by cooperative effects, increasing the acidity of the hydrogen cyanide H atom involved in the π H-bond. The longer HCN chains (n ≥ 3), however, can bend to form CH/N H-bonds with the Bz H atoms. These cyclic structures are found to be slightly more stable than their linear counterparts. For the nonlinear Bz(HCN)(3-4) and Bz(H(2)O)(2-4) complexes, an increase of the binding energy with the number of solvent molecules and a decrease of the IE of benzene, relative to the values for the Bz(HCN) and Bz(H(2)O) complexes, respectively, are observed. Although a strengthening of the CH/π and OH/π H-bonds, with increasing n, also takes place for the Bz(H(2)O)(2-4) and Bz(HCN)(3-4) nonlinear complexes, Bz proton donor, CH/O, and CH/N interactions are at the origin of this decrease. Thus CH/π and OH/π H-bonds lead to higher IEs of Bz, whereas the weaker CH/N and CH/O H-bond interactions have the opposite effect. The present results emphasize the importance of both aromatic XH/π (X = C, O) and CH/X (X = N, O) interactions for understanding the structure and electronic properties of Bz(HCN)(n) and Bz(H(2)O)(n) complexes.     

Equilibrium of low- and high-spin states of Ni(II) complexes controlled by the donor ability of the bidentate ligands

Low-spin nickel(II) complexes containing bidentate ligands with modulated nitrogen donor ability, Py(Bz)2 or MePy(Bz)2 (Py(Bz)2 = N,N-bis(benzyl)-N-[(2-pyridyl)methyl]amine, MePy(Bz)2 = N,N-bis(benzyl)-N-[(6-methyl-2-pyridyl)methyl]amine), and a beta-diketonate derivative, tBuacacH (tBuacacH = 2,2,6,6-tetramethyl-3,5-heptanedione), represented as [Ni(Py(Bz)2)(tBuacac)](PF6) (1) and [Ni(MePy(Bz)2)(tBuacac)](PF6) (2) have been synthesized. In addition, the corresponding high-spin nickel(II) complexes having a nitrate ion, [Ni(Py(Bz)2)(tBuacac)(NO3)] (3) and [Ni(MePy(Bz)2)(tBuacac)(NO3)] (4), have also been synthesized for comparison. Complexes 1 and 2 have tetracoordinate low-spin square-planar structures, whereas the coordination environment of the nickel ion in 4 is a hexacoordinate high-spin octahedral geometry. The absorption spectra of low-spin complexes 1 and 2 in a noncoordinating solvent, dichloromethane (CH2Cl2), display the characteristic absorption bands at 500 and 540 nm, respectively. On the other hand, the spectra of a CH2Cl2 solution of high-spin complexes 3 and 4 exhibit the absorption bands centered at 610 and 620 nm, respectively. The absorption spectra of 1 and 2 in N,N-dimethylformamide (DMF), being a coordinating solvent, are quite different from those in CH2Cl2, which are nearly the same as those of 3 and 4 in CH2Cl2. This result indicates that the structures of 1 and 2 are converted from a low-spin square-planar to a high-spin octahedral configuration by the coordination of two DMF molecules to the nickel ion. Moreover, complex 1 shows thermochromic behavior resulting from the equilibrium between low-spin square-planar and high-spin octahedral structures in acetone, while complex 2 exists only as a high-spin octahedral configuration in acetone at any temperature. Such drastic differences in the binding constants and thermochromic properties can be ascribed to the enhancement of the acidity of the nickel ion of 2 by the steric effect of the o-methyl group in the MePy(Bz)2 ligand in 2, which weakens the Ni-N(pyridine) bond length compared with that of the nonsubstituted Py(Bz)2 ligand in 1.     

Density functional theory studies of inorganic metallocene multidecker V(n)(P(6))(n+1) (n=1-4) sandwich clusters

Motivated by the synthesis of the first entirely inorganic metallocene sandwich ion [eta(5)-Ti-(P(5))(2)](2-) [E. Urnezius et al. Science 295, 832 (2002)], we have designed a new inorganic metallocene sandwich [eta(6)-V-(P(6))(2)] and multidecker sandwich clusters up to V(4)(P(6))(5) by employing an all electron gradient-corrected density functional theory. The binding energies of the V(n)(P(6))(n+1) complexes increase rapidly from half sandwich to the smallest full sandwich and become gradually afterwards. The highest occupied and lowest unoccupied molecular orbital gap and the vertical ionization energy decrease with increasing cluster size. The V(n)(P(6))(n+1) clusters are nonferromagnetic and prefer the lowest available spin states. The smallest sandwich cluster, V(P(6))(2), has the high stability and might serve as a building block for one-dimensional inorganic polymers with high stabilities.     

Dual coordination modes of ethylene-linked NP2 ligands in cobalt(II) and nickel(II) iodides

Here we report the syntheses and crystal structures of a series of cobalt(II) and nickel(II) complexes derived from (R)NP2 ligands (where R = OMe(Bz), H(Bz), Br(Bz), Ph) bearing ethylene linkers between a single N and two P donors. The Co(II) complexes generally adopt a tetrahedral configuration of general formula [(NP2)Co(I)(2)], wherein the two phosphorus donors are bound to the metal center but the central N-donor remains unbound. We have found one case of structural isomerism within a single crystal structure. The Co(II) complex derived from (Bz)NP2 displays dual coordination modes: one in the tetrahedral complex [((Bz)NP2)Co(I)(2)]; and the other in a square pyramidal variant, [((Bz)NP2)Co(I)(2)]. In contrast, the Ni(II) complexes adopt a square planar geometry in which the P(Et)N(Et)P donors in the ligand backbone are coordinated to the metal center, resulting in cationic species of formula [((R)NP2)Ni(I)](+) with iodide as counterion. All Ni(II) complexes exhibit sharp (1)H and (31)P spectra in the diamagnetic region. The Co(II) complexes are high-spin (S = 3/2) in the solid state as determined by SQUID measurements from 4 to 300 K. Solution electron paramagnetic resonance (EPR) experiments reveal a high-spin/low-spin Co(II) equilibrium that is dependent on solvent and ligand substituent.     

Synthesis and structural characterization of sterically crowded hydridotris(pyrazolyl)borato complexes: Unusual double 1,2-borotropic shift at a titanium centre

The potassium and thallium(I) derivatives of the hydrido-tris(3-Me₂Bz,5-Me-pyrazol-1-yl)borato ligand, K[Tp^Me2^Bz,Me] (1) and Tl[Tp^Me2^Bz,Me] (2), are reported. Their reactions with TiCl₄ under mild conditions afforded, after rearrangement of the ligand, recognized as a double 1,2-borotropic shift, the related Ti(IV) complex {hydrido-[bis(3-Me,5-Me₂Bz)(3-Me₂Bz,5-Me)-pyrazol-1-yl]borato}trichlorotitanium(IV), [Tp^Me2^Bz,Me∗∗] TiCl₃ (3). The ¹H- and ¹³C NMR spectra of the new compounds are discussed, the molecular structure of 3 has been determined by X-ray diffraction methods, the titanium centre has a pseudo-octahedral coordination, with the nitrogen and chloride ligands in a fac geometry. A possible mechanism of formation of 3 is proposed.     

Ab initio calculations of anharmonic vibrational spectroscopy for hydrogen fluoride (HF)n (n = 3, 4) and mixed hydrogen fluoride/water (HF)n(H2O)n (n = 1, 2, 4) clusters

Anharmonic vibrational frequencies and intensities are computed for hydrogen fluoride clusters (HF)n, with n = 3, 4 and mixed clusters of hydrogen fluoride with water (HF)n(H2O)n where n = 1, 2. For the (HF)4(H2O)4 complex, the vibrational spectra are calculated at the harmonic level, and anharmonic effects are estimated. Potential energy surfaces for these systems are obtained at the MP2/TZP level of electronic structure theory. Vibrational states are calculated from the potential surface points using the correlation-corrected vibrational self-consistent field method. The method accounts for the anharmonicities and couplings between all vibrational modes and provides fairly accurate anharmonic vibrational spectra that can be directly compared with experimental results without a need for empirical scaling. For (HF)n, good agreement is found with experimental data. This agreement shows that the M?ller-Plesset (MP2) potential surfaces for these systems are reasonably reliable. The accuracy is best for the stiff intramolecular modes, which indicates the validity of MP2 in describing coupling between intramolecular and intermolecular degrees of freedom. For (HF)n(H2O)n experimental results are unavailable. The computed intramolecular frequencies show a strong dependence on cluster size. Intensity features are predicted for future experiments.     

Geometric and electronic structures of multiple-decker one-end open sandwich clusters: Eu(n)(C8H8)n- (n = 1-4)

We have measured the photoelectron spectra of the multiple-decker 1:1 sandwich clusters of Eu(n)(COT)n- (n = 1-4; COT = 1,3,5,7-cyclooctatetraene), synthesized in the gas phase, and studied theoretically the bonding scheme, charge distribution, valence orbital energies, and photodetachment energies. We calculated the ground electronic state X- and the first excited electronic state A-, both of which have strong ionic bonding and a characteristic charge distribution. Moreover, we found that the valence orbital energies of Eu (6s) and COT (L delta) depend strongly on cluster size and their positions in the clusters. With the calculated vertical detachment energies for these valence orbitals, we assigned the peaks in the experimental photoelectron spectra and analyzed the origin of their interesting behavior by employing simple point charge models. From these analyses, it became clear that the characteristic behavior of the spectra is due to the strong ionic bonding and the charge distribution. In addition, using the point charge models, we estimated the vertical detachment energies of the one-dimensional polymer [Eu(COT)]infinity-.     

Syntheses, crystal and molecular structures, and properties of some new phenylmercury(II) dithiolate complexes

A series of new phenylmercury(ii) dithio complexes [PhHg(Bu(n)(2)dtc)] (; Bu(n)(2)dtc(-) = di-n-butyldithiocarbamate), [PhHg(morphdtc)] (; morphdtc(-) = morpholinedithiocarbamate), [PhHg(Bz(2)dtc)] (; Bz(2)dtc(-) = dibenzyldithiocarbamate), [PhHg(methoxethxant)] (; methoxethxant(-) = 2-methoxyethylxanthate) [(PhHg)(2)NED] (; NED(2-) = 1-nitroethylene-2,2-dithiolate) and [(PhHg)(2)CDC] (; CDC(2-) = cyanodithioimidocarbonate) have been prepared and characterized by elemental analysis, UV-Vis, IR, (1)H and (13)C NMR spectra and mass spectrometry. The crystal structures of , and showed a linear Hg(ii) core at the center of the molecules. The weak intra- and intermolecular HgS interactions provide a molecular chain framework. The reaction of PhHgO(2)CCH(3) with Bu(n)(2)dtcH gave the known dimeric complex Hg(Bu(n)(2)dtc)(2) while the Ni(O(2)CCH(3))(2) mediated reaction gave instead of the expected heterobimetallic complex [PhHgNi(Bu(n)(2)CS(2))(2)]O(2)CCH(3) which has been corroborated by natural charges at each atom obtained at the density functional level (DFT) of theory. Upon excitation at 358 nm exhibited a medium strong photoluminescence emission at 420 nm as a consequence of intraligand pi --> pi* transitions. The electronic absorption bands of were assigned from time dependent density functional theory (TD-DFT) calculations. Geometrical configurations of , and have been optimized using the DFT method. All of the complexes are weakly conducting (sigma(rt) approximately 10(-12) S cm(-1)). However and exhibited semiconductivity with band gaps of 0.39 and 0.94 eV respectively.     

Structure and magnetism of VnBz(n+1) sandwich clusters

Results on structural, energetic, electronic, and magnetic properties of linear sandwich VnBzn+1 clusters obtained using high-accuracy density functional computations are presented and analyzed. Energetically close-lying configurations and states of different spin-multiplicities are identified. The computed characteristics are in good agreement with the available experimental data. The computations predict that the most stable forms of the clusters in the size range n >/= 4 are chiral. This feature, combined with the magnetism of these systems, makes them of potential importance as building blocks of nanosystems with coupled optical and magnetic functionalities.     

Structure and stability of (TiO2)n, (SiO2)n, and mixed Ti(m)Si(n-m)O(2n) [n = 2-5, m = 1 to (n - 1)] clusters

Structures, energetics, and vibrational spectra are investigated for small pure (TiO(2))(n), (SiO(2))(n), and mixed Ti(m)Si(n-m)O(2n) [n = 2-5, m = 1 to (n - 1)] oxide clusters by density functional theory (DFT). The BP86/ATZP level of theory is employed to obtain constitutional isomers of the oxide clusters. In accordance with previous studies, our calculations show three-dimensional compact structures are preferred for pure (TiO(2))(n) with oxo-stabilized higher hexavalent states, and linear chain structures are favored for pure (SiO(2))(n) with tetravalent states. However, the herein theoretically first reported mixed Ti(m)Si(n-m)O(2n) oxide clusters prefer either three-dimensional compact or linear chain structures depending upon the stoichiometry of the compound. Vibrational analysis of the important modes of some highly stable structures is provided. Coupled-cluster single and double excitation (with triples) [CCSD(T)] computed energy gaps for the TiO(2) dimers compare well with results from previous study. Excitation energies are computed by use of time-dependent (TD) DFT and equation-of-motion coupled-cluster calculations with singles and doubles (EOM-CCSD) for the most stable isomers.     

Donor-acceptor-substituted tetrakis(phenylethynyl)benzenes as emissive molecules during pulse radiolysis in benzene

Emission from charge recombination between radical cations and anions of various tetrakis(phenylethynyl)benzenes (TPEBs) was measured during pulse radiolysis in benzene (Bz). The formation of TPEB in the singlet excited state (1TPEB*) can be attributed to the charge recombination between TPEB*+ and TPEB*-, which are initially generated from the radiolytic reaction in Bz. This mechanism is reasonably explained by the relationship between the annihilation enthalpy change (-DeltaH degrees) for the charge recombination of TPEB*+ and TPEB*- and excitation energy of 1TPEB*. It was found that the charge recombination between TPEB*+ and TPEB*- occurred to give 1TPEB* as the emissive species, but not the excimers because of the large repulsion between substituents caused by the rotation around C-C single bonds of TPEBs. Since donor-acceptor-substituted TPEBs possess three types of charge-transfer pathways (linear-conjugated, cross-conjugated, and "bent" conjugated pathways between the donor and acceptor substituents through the ethynyl linkage), the emission spectra of 1TPEBs* with intramolecular charge transfer (ICT) character depend on the substitution pattern and the various kinds of donor and acceptor groups during pulse radiolysis in Bz.     

Phosphine-ligated induced formation of thallium(I) full Pt3TlPt3 sandwich versus "open-face" TlPt3 sandwich with triangular Pt3(mu2-CO)3(PR3)3 units: synthesis and structural/spectroscopic analysis of triphenylphosphine [(mu3-Tl)Pt3(mu2-CO)3(PPh3)3]+ and its (mu3-AuPPh3)Pt3 analogue

This research constitutes an operational test to assess the influence of platinum-attached phosphine ligands in the formation process of "open-face" TlPt3 or "full" Pt3TlPt3 sandwich clusters. Accordingly, the reaction of TlPF6 with triphenylphosphine Pt4(mu2-CO)5(PPh3)4, under essentially identical boundary conditions originally used to prepare (90% yield) the triethylphosphine "full" Pt3TlPt3 sandwich, [(mu6-Tl)Pt6(mu2-CO)6(PEt3)6]+ (3) ([PF6]- salt), from Pt4(mu2-CO)5(PEt3)4 was carried out to see whether it would likewise afford the unknown triphenylphosphine Pt3TlPt3 sandwich analogue of or whether the change of phosphine ligands from sterically smaller, more basic PEt3 to PPh3 would cause the product to be the corresponding unknown triphenylphosphine "open-face" TlPt3 sandwich that would geometrically resemble the known bulky tricyclohexylphosphine [(mu3-Tl)Pt3(mu2-CO)3(PCy3)3]+ sandwich (2a). Both the structure and composition of the resulting "open-face" sandwich product, [(mu3-Tl)Pt3(mu2-CO)3(PPh3)3]+ (1a) ([PF6]- salt), were unequivocally established from a low-temperature CCD X-ray crystallographic determination. The calculated Pt/Tl atom ratio (3/1) of 75%/25% is in excellent agreement with that of 72(3)%/28(5)% obtained from energy-resolved measurements on a single crystal with a scanning electron microscope. Crystals (80% yield) of the orange-red were characterized by solid-state/solution IR and variable temperature 205Tl and 31P{1H} NMR spectra; the 31P{1H} spectra provide convincing evidence that is exhibiting dynamic behavior at room temperature in CDCl3 solution. The corresponding new "open-face" (mu3-AuPPh3)Pt3 sandwich, [(mu3-AuPPh3)Pt3(mu2-CO)3(PPh3)3]+ (1b) ([PF6]- salt), was quantitatively obtained from by reaction with AuPPh3Cl and spectroscopically characterized by IR and 31P{1H} NMR spectra. A comparative geometrical evaluation of the observed steric dispositions of the platinum-attached PR3 ligands in the "open-face" (mu3-Tl)Pt3 sandwiches of (with PPh3) and the known (with PCy3) and in the known "full" Pt3TlPt3 sandwich of (with PEt3) along with the considerably different observed steric dispositions of the PR(3) ligands in the known "open-face" (mu3-AuPCy3)Pt3 sandwich of (with PCy3) and in the known "full" Pt3AuPt3 sandwich of (with PPh(3)) has been performed. The results clearly indicate that, in contradistinction to the known triphenylphosphine Pt3AuPt3 sandwich of , PPh3 and bulkier PCy3 ligands of Pt3(mu2-CO)3(PR3)3 units are sterically too large to form "full" Pt3TlPt3 sandwiches. In other words, the nature of the thallium(I) sandwich-product in these reactions is sterically controlled by size effects of the phosphine ligands. Comparative examination of bridging carbonyl IR frequencies of and with those of closely related "open-face" and "full" sandwiches provides better insight concerning the relative electrophilic capacities of Tl+, Au+, and [AuPR3]+ components in forming sandwich adducts with Pt3(mu2-CO)3(PR3)3 nucleophiles.     

Magnetic couplings in vanadium aromatic sandwich complexes and their crystals by using DFT methods

Using density functional theory, we have theoretically studied the origin of ferromagnetic coupling of spins in the long multiple deckers of vanadium sandwich complexes with benzene (Bz). This is done by calculating the band structure of their infinite one-dimensional (1D) crystals along the periodic (=Z) direction. We find that the magnetic coupling can be ascribed to spin polarization in the band (= those derived from d(z2)) whose k states are not involved in the formation of partial covalent bonds between vanadium atoms and benzene rings. We have also studied magnetic and electronic properties of multiple deckers of a naphthalene (Np)-vanadium complex. We find that there is a stronger covalent interaction as well as a stronger electrostatic interaction between V and Np rings than between V and Bz rings. This suggests that there is a possibility of longer multiple deckers of a Np-V complex. In addition, ferrimagnetic coupling of spins is expected, resulting in a magnetic moment 45% larger than that of the Bz-V complex at the same length. For their 1D crystals, band structure analysis also shows that the origin of magnetic coupling in long multiple deckers should be similar to that of Bz-V multiple deckers.     

Infrared spectra and ab initio calculations for the Cl--(CH4)n (n = 1-10) anion clusters

In an effort to elucidate their structures, mass-selected Cl--(CH4)n (n = 1-10) clusters are probed using infrared spectroscopy in the CH stretch region (2800-3100 cm(-1)). Accompanying ab initio calculations at the MP2/6-311++G(2df,2p) level for the n = 1-3 clusters suggest that methane molecules prefer to attach to the chloride anion by single linear H-bonds and sit adjacent to one another. These conclusions are supported by the agreement between experimental and calculated vibrational band frequencies and intensities. Infrared spectra in the CH stretch region for Cl--(CH4)n clusters containing up to ten CH4 ligands are remarkably simple, each being dominated by a single narrow peak associated with stretching motion of hydrogen-bonded CH groups. The observations are consistent with cluster structures in which at least ten equivalent methane molecules can be accommodated in the first solvation shell about a chloride anion.