Temperature dependence of trapped electrons in crystalline D2O ice from 77 to 6 k

The temperature dependence of the abundance of trapped electrons which absorb in the visible (e^?_vis) and infrared (e^?_IR) in crystalline D₂O ice has been studied by pulse radiolysis between 77 and 6 k. The yield (G) and decay of e^?_vis show little dependence on temperature or doping with NH₄F. At 6 K G(e^?_vis) is 0.54 and the electron decays by half within 5 μs. These observations are consistent with e^?_vis being mainly located in spurs. The yield and decay of e^?_IR, on the other hand, show a more marked dependence on temperature. In the pure crystal G(e^?_IR) increases more than tenfold from ≈ 0.1 at 77 K to 1.3 at 6 K and its decay rate is greatly decreased at the lower temperature. Doping with NH₄F increases G(e^?_IR) to 0.85 to 77 K and to 1.8 at 6 K and some decay is observed at 6 K but not at 77 K. These results are interpreted on the basis that geminate recombination between electrons and holes is very fast at 77 K but becomes sufficiently slow for the electrons to be observed at 6 K. It is also inferred that the hole is more mobile than e^?_IR. The mechanisms causing the decays of e^?_vis and e^?_IR are discussed.     

Near-IR absorption spectrum of the solvated electron in alcohols and deuterated water

The absorption band profiles of the solvated electron in aqueous and alcohol glasses at 77, 115 and 300 K were calculated in terms of the theory presented in our previous paper [J. Phys. Chem.95, 6149 (1991)]. We have concentrated our attention on the problem of the IR-absorbing electrons (e^-_IR) trying to explain their appearance in alcohols, deuterated water and their lack in H₂O at low temperatures. The comparison between the experiment and the theoretical model provides new arguments to the discussion on the initial spectra of trapped electrons.     

Nanosecond laser measurements of optical absorption coefficients of electrons in polar fluids

Direct measurements of the optical absorption coefficients of the short-lived electrons in polar fluids have been made. Laser-induced photoionization of pyrene in alcohols at 293 K generated equal numbers of electrons (e_s^?) and pyrene positive ions (P⁺). The ?_max(e_s^?) were derived by measuring the relative absorption intensities of e_s^? and P⁺, which had been independently characterised. The ?_max values for e_s^? in methanol to 1-decanol fell within the range (1.0–2.0) × 10⁴ M^?1 cm^?1, the implications of which are discussed.     

Oxidative addition reactions of [Pt(CN)4]2−; A 13C and 195Pt NMR study

¹³C and ¹⁹⁵Pt NMR measurements show that complexes of the type trans-[Pt(CN)₄X₂]^2? are formed on addition of X₂ (X = Br, Cl, I) to M₂[Pt(CN)₄] (M = K or NBu₄) in aqueous and chloroform solution respectively. Addition of ICN to K₂[Pt(CN)₄] (60% ¹³CN^?) in aqueous solution results in the formation of potassium pentacyanoiodoplatinate(IV) with complete¹³CN^?/¹²CN^?scrambling. The reaction of equi-molar amounts of trans-[PtX₂(CN)₄]^2? (X = Br and Cl), which was previously claimed to result in complete transformation into trans-[PtBrCl(CN)₄]^2?, is instead shown to result in an approximately statistical redistribution of halogens. A progressive shift of δ_Pt to high field is observed on successive replacement of ¹²CN^? by ¹³CN^? in [Pt(CN)₄]^2?.     

Synthesis,structure, and kinetic studies on [RuCl2(NCCH3)2(cod)]

[RuCl₂(NCCH₃)₂(cod)], an alternative starting material to [RuCl₂(cod)] _n for the preparation of ruthenium(II) complexes, has been prepared from the polymer compound and isolated in yields up to 87% using a new work-up procedure. The compound has been obtained as a yellow solid without water of crystallization. The complexes [RuCl₂(NCR)₂(cod)] spontaneously transform into dimers [Ru₂Cl(μ-Cl)₃(cod)₂(NCR)] (R?=?Me, Ph). ¹H NMR kinetic experiments for these transformations evidenced first-order behavior. [RuCl₂(NCPh)₂(cod)] dimerizes slower by a factor of ten than [RuCl₂(NCCH₃)₂(cod)]. The following activation parameters, ΔH ^#?=?114?±?3?kJ?mol^?1 and ΔS ^#?=?66?±?9?J?K^?1?mol^?1 for R?=?CH₃CN (ΔG ^#?=?94?±?5?kJ?mol^?1, 298.15?K) and ΔH ^#?=?122?±?2?kJ?mol^?1 and ΔS ^#?=?75?±?6?J?K^?1?mol^?1 for R?=?Ph (ΔG ^#?=?100?±?4?kJ?mol^?1, 298.15?K), have been calculated from the first-order rate constants in the temperature range 294–323?K. The kinetic parameters are in agreement with a two-step mechanism with dissociation of acetonitrile as the rate-determining step. The molecular structures of [Ru₂Cl(μ-Cl)₃(cod)₂(NCR)] (R?=?Me, Ph) have been determined by X-ray diffraction.     

Nonequilibrium vibrational populations and dissociation rates of oxygen in electrical discharges

Nonequilibrium vibrational distributions and dissociation rates of molecular oxygen in both electrical and thermal conditions have been calculated by solving a system of master equations including V-V (vibration-vibration), V-T (vibration-translation) and e-V (electron-vibration) energy exchanges. The dissociation constant under thermal conditions (i.e. without electrons) follows an Arrhenius law with an activation energy of 120 kcal/mole, while the corresponding rates under electrical conditions (5000 ? T_e ? 15000 K, 300 ? T_g ? 1000 K, 10¹¹ ? n_e ? 10¹² cm^?3,5 ? p ? 20 torr) increase with decreasing gas (T_g) and electron (T_e) temperatures and pressure (p) and with increasing electron density (n_e). These results are explained on the basis of the different interplay of V-V and V-T energy exchanges and are rationalized by means of simplified models proposed in the literature. The accuracy of the present results is discussed paying particular attention to the dependence of V-V and V-T rate coefficients on the vibrational quantum number. A comparison of the calculated dissociation rates with the corresponding ones obtained by the direct electron impact mechanism shows that the present mechanism prevails at low electron and gas temperatures. Finally a comparison is shown between theoretical and experimental dissociation rates under electrical and thermal conditions.     

Solvation of ions. XXVII. Comparison of methods to calculate single ion free energies of transfer in mixed solvents

Free energies of transfer of ions from water to mixtures of water with acetonitrile (AN), with dimethylformamide (DMF), with dimethylsulfoxide (DMSO), and with ethylene glycol have been determined using both the tetraphenylarsonium tetraphenylboride [TATB] and the negligible liquid junction potential [E _j ] assumptions. By making use of ΔG _tr (Ag⁺)[TATB]=12 kJ-mol^?1 for transfer from DMSO to AN and by assuming negligible liquid junction potential in the cell $${\text{Ag|AgNO}}_{\text{3}} {\text{(0}}{\text{.01}}M{\text{),S}}\parallel {\text{Et}}_{\text{4}} {\text{NPic(0}}{\text{.1}}M{\text{),AN}}\parallel {\text{AgNO}}_{\text{3}} {\text{(0}}{\text{.01}}M{\text{),AN|Ag}}$$ single ion free energies of transfer of silver ion ΔG _tr (Ag⁺)[E _j ] from DMSO to 35 pure and mixed solvents show a standard deviation of only 2 kJ-mol^?1 when compared with ΔG _tr (Ag⁺) calculated from the TATB assumption that ΔG _tr (Ph ₄ As⁺)=ΔG _tr (Ph ₄ B^?). The ferrocene assumption [Fc] also gives acceptable agreement with ΔG _tr (Ag⁺)[TATB] provided that the solvents are not highly aqueous. Other cells with other junctions give less acceptable agreement between the E _j and TATB assumptions. It is essential that the salt bridge is always tetraethylammonium picrate in AN, if the E _j assumption is assumed. Because of the ease of making potentiometric measurements compared with the difficulty of measurements required for the TATB assumption, the negligible liquid junction potential method in the cell shown is recommended for estimating transfer free energies of single ions. The ferrocene assumption is acceptable only for non-structured aprotic solvents.     

Electrochemical Investigations Give Some Insights into the Coordination Chemistry of New Stable Iridium(+1), Iridium(0), and Iridium(−1) Complexes

The redox chemistry of the stable tetracoordinated 16 valence electron d⁸‐[Ir^+I(tropp^Ph)₂]⁺(PF₆)^? and pentacoordinated 18 valence d⁸‐[Ir^+I(tropp^Ph)₂Cl] complexes was investigated by cyclic voltammetry (tropp^Ph=dibenzotropylidenyl phosphine). The experiments were performed using a platinum microelectrode varying scan rates (100 mV/s–10 V/s) and temperatures (? 40 to 20 °C) in tetrahydrofuran, THF, or acetonitrile, ACN, as solvents. In THF, the overall two‐electron reduction of the 16 valence electron d⁸‐[Ir^+I(tropp^Ph)₂]⁺(PF₆)^? proceeds in two well separated slow heterogeneous electron transfer steps according to: d⁸‐[Ir^+I (tropp^Ph)₂]⁺+e^?→d⁹‐[Ir⁰(tropp^Ph)₂]+e^?→d¹⁰‐[Ir^?I(tropp^Ph)₂]^?, [k^s₁=2.2×10^?3 cm/s for d⁸‐Ir^+I/d⁹‐Ir⁰ and k^s₂=2.0×10^?3 cm/s for d⁹‐Ir⁰/d¹⁰‐Ir^?I]. In ACN, the two redox waves merge into one “two‐electron” wave [k^s_1,2=7.76×10^?4 cm/s for d⁸‐Ir^+I/d⁹‐Ir⁰ and d⁹‐Ir⁰/d¹⁰‐Ir^?I] most likely because the neutral [Ir⁰(tropp^Ph)₂] complex is destabilized. At low temperatures (ca. ? 40 °C) and at high scan rates (ca. 10 V/s), the two‐electon redox process is kinetically resolved. In equilibrium with the tetracoordianted complex [Ir^+I(tropp^Ph)₂]⁺ are the pentacoordinated 18 valence [Ir^+I(tropp^Ph)₂L]⁺ complexes (L=THF, ACN, Cl^?) and their electrochemical behavior was also investigated. They are irreversibly reduced at rather high negative potentials (? 1.8 to ? 2.4 V) according to an ECE mechanism 1) [Ir^+I(tropp^Ph)₂(L)]+e^?→[Ir⁰(tropp^Ph)₂(L)]; 2) [Ir⁰(tropp^Ph)₂(L)]→[Ir(tropp^Ph)₂]+L, iii) [Ir⁰(tropp^Ph)₂]+e^?→[Ir^?I(tropp^Ph)₂]^?. Since all electroactive species were isolated and structurally characterized, our measurements allow for the first time a detailed insight into some fundamental aspects of the coordination chemistry of iridium complexes in unusually low formal oxidation states.     

Solvent extraction of europium trifluoromethanesulfonate into nitrobenzene in the presence of p-tert-butylcalix[6]arene and p-tert-butylcalix[8]arene

From extraction experiments and ??-activity measurements, the extraction constants corresponding to the general equilibrium Eu³⁺(aq) + 3A^?(aq) + L(nb) ? EuL³⁺(nb) + 3A^?(nb) taking part in the two-phase water?Cnitrobenzene system (A^? = CF₃SO₃ ^?; L = p-tert-butylcalix[6]arene, p-tert-butylcalix[8]arene; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the EuL³⁺ complexes in nitrobenzene saturated with water were calculated for a temperature of 25 °C as log ?? _nb(EuL³⁺) = 6.4 ± 0.1 (L = p-tert-butylcalix[6]arene) and log ?? _nb(EuL³⁺) = 11.3 ± 0.1 (L = p-tert-butylcalix[8]arene).     

Behavior of nitrite forms of nitrosylruthenium on extraction and back extraction of heterometalic Ru/Zn complexes with trioctylphosphine oxide

The state of ruthenium in conjugated phases upon extraction of trans-[Ru(¹⁵NO)(¹⁵NO₂)₄(OH)]^2? complex with tri-n-octylphosphine oxide (TOPO) in the presence of Zn²⁺ and subsequent back extraction with H¹⁵NO₃ and NH₃(concd.) solutions was studied by ¹⁵N NMR. Binuclear complexes [Ru(NO)(NO₂)_5?n (μ-NO₂) _n?1(μ-OH)Zn(TOPO) _n ] and [Ru(NO)(NO₂)_4?n (ONO)(μ-NO₂) _n?1(μ-OH)Zn(TOPO) _n ], where n = 2, 3, are predominant forms in extract. Kinetic restrictions for ruthenium extraction with TOPO solution in hexane and its back extraction with aqueous solutions of nitric acid and ammonia are eliminated in the absence of direct coordination of extractant to ruthenium. fac-Dinitronitrosyl forms [Ru(NO)(H₂O)₃(NO₂)₂]⁺, [Ru(NO)(H₂O)₂(NO₂)₂(NO₃)]⁰ (3 and 6 M HNO₃) and [Ru(NO)(H₂O)(NO₂)₂(NO₃)₂]^? (6 M HNO₃) prevail in nitric acid back extracts. Equilibrium constant at ambient temperature (0.05 ± 0.01) was assessed for the coordination of second nitrate ion to nitrosylruthenium dinitronitrato complex. Complex species [Ru(NO)(NO₂)₄(OH)]^2? and [Ru(NO)(NO₂)₃(ONO)(OH)]^2? prevail in ammonia back extract.     

Chelation versus Binucleation: Metal Complex Formation with the Hexadentate all‐cis‐N1,N2‐Bis(2,4,6‐trihydroxy‐3,5‐diaminocyclohexyl)ethane‐1,2‐diamine

The hexadentate ligand all‐cis‐N¹,N²‐bis(2,4,6‐trihydroxy‐3,5‐diaminocyclohexyl)ethane‐1,2‐diamine (L^e) was synthesized in five steps with an overall yield of 39 % by using [Ni(taci)₂]SO₄?4 H₂O as starting material (taci=1,3,5‐triamino‐1,3,5‐trideoxy‐cis‐inositol). Crystal structures of [Na_0.5(H₆L^e)](BiCl₆)₂Cl_0.5?4 H₂O ( 1 ), [Ni(L^e)]‐ Cl₂?5 H₂O ( 2 ), [Cu(L^e)](ClO₄)₂?H₂O ( 3 ), [Zn(L^e)]CO₃?7 H₂O ( 4 ), [Co(L^e)](ClO₄)₃ ( 5 c ), and [Ga(H_?2L^e)]‐ NO₃?2 H₂O ( 6 ) are reported. The Na complex 1 exhibited a chain structure with the Na⁺ cations bonded to three hydroxy groups of one taci subunit of the fully protonated H₆(L^e)⁶⁺ ligand. In 2 , 3 , 4 , and 5 c , a mononuclear hexaamine coordination was found. In the Ga complex 6 , a mononuclear hexadentate coordination was also observed, but the metal binding occurred through four amino groups and two alkoxo groups of the doubly deprotonated H_?2(L^e)^2?. The steric strain within the molecular framework of various M(L^e) isomers was analyzed by means of molecular mechanics calculations. The formation of complexes of L^e with Mn^II, Cu^II, Zn^II, and Cd^II was investigated in aqueous solution by using potentiometric and spectrophotometric titration experiments. Extended equilibrium systems comprising a large number of species were observed, such as [M(L^e)]²⁺, protonated complexes [MH_z(L^e)]^2+z and oligonuclear aggregates. The pK_a values of H₆(L^e)⁶⁺ (25 °C, μ=0.10 m ) were found to be 2.99, 5.63, 6.72, 7.38, 8.37, and 9.07, and the determined formation constants (log β) of [M(L^e)]²⁺ were 6.13(3) (Mn^II), 20.11(2) (Cu^II), 13.60(2) (Zn^II), and 10.43(2) (Cd^II). The redox potentials (vs. NHE) of the [M(L^e)]^3+/2+ couples were elucidated for Co (?0.38 V) and Ni (+0.90 V) by cyclic voltammetry.     

Synthesis and characterization of microstructured sheets of semiconducting Ca[TCNQ]2 via redox-driven solid-solid phase transformation of TCNQ microcrystals

Microstructured sheets of semiconducting Ca[TCNQ]₂ (TCNQ = 7,7,8,8-tetracyanoquinodimethane) have been synthesized via electrochemically driven (TCNQ)/Ca[TCNQ]₂ solid-solid phase transformation that occurs upon one-electron reduction of solid TCNQ, mechanically attached to an electrode surface, in the presence of an aqueous Ca²⁺ _(aq) electrolyte solution. Voltammetric probing of the electrochemically irreversible TCNQ/Ca[TCNQ]₂ interconversion revealed that it is highly dependent on scan rate and Ca²⁺ _(aq) electrolyte concentration. This voltammetric behavior, supported by double potential-step chronoamperometric evidence, clearly attests that formation of Ca[TCNQ]₂ takes place via a rate-determining nucleation/growth process, which involves ingress of Ca²⁺ _(aq) cations into the TCNQ^·? crystal lattice at the triple phase TCNQ/TCNQ^·? _(s)│GC_(s)│Ca²⁺ _(aq) electrolyte junction. The overall redox process associated with this chemically reversible solid-solid transformation can be described by the equation: TCNQ⁰ _(S)?+?2e^??+?Ca²⁺ _(aq) ? {Ca[TCNQ]₂}_(S). SEM characterization of the morphology of the generated Ca[TCNQ]₂ material showed the formation of microstructured sheets, which are substantially different from those of parent TCNQ crystals and the needle-shaped crystals of group I cations (M⁺?=?Li, Na, K, Rb, and Cs). The kinetic and thermodynamic implications of the ΔE _p and E _m values as a function of scan rate are discussed in terms of nucleation–growth and their relevance to those reported for the conceptually related group I cations and binary M[TCNQ]₂ (M²⁺?=?Mn, Fe, Co, and Ni)-based coordination polymers.     

Radiation-chemical processes as disclosure of electronic states in a bis(dinitrogen) molybdenum complex

On the basis of experimental data the energy levels of the central-atom orbitals in the complex [Mo(N₂)₂(dppe)₂] [dppe = 1,2-bis(diphenylphosphine)ethane] were calculated. Using the diagram thus obtained the eletronic configuration of the irradiation-generated ion, [Mo(N₂)₂(dppe)₂]⁻, was determined to be as follows: (b_2g)² (e_g)⁴ (b_1g)¹ or (b_2g)² (e_g)⁴ (e_u). The yields from the decomposition of [Mo(N₂)₂(dppe)₂] in the solid phase in a hydrogen atmosphere were determined on the basis of the decrease in band intensities at 306 and 377 nm: G(− MoN₂)_306nm = 0.01, and G(− MoP)_377nm = 0.1 (molecules per 100 eV). In toluene solution it was found that G(− MoN₂) > G(− MoP). The yields observed were in accordance with the calculated levels. Using a mass spectrometer the volatile products of [Mo(N₂)₂(dppe)₂] radiolysis in H₂ and O₂ atmospheres were identified as H₃N, H₄N₂, NO and N₂O. In the light of the results mentioned above (as well as the IR results) a mechanism for the radiolysis of [Mo(N₂)₂(dppe)₂] in the solid phase was proposed.     

Potential energy curves for ground and excited states of NaLi from ab initio calculations with effective core polarization potentials

Sixteen low-lying electronic states of NaLi are investigated by SCF/valence Cl calculations including core polarization effects by means of an effective potential. Spectroscopic constants are obtained with estimated uncertainties of ΔR_e ? 0.01 Å, Δω_e ? 0.6 cm^?1 and ΔD_e ? 80 cm^?1. From a comparison of experimental and theoretical G(υ) values, we suggest a ground-state dissociation energy of 7093 ± 5 cm^?1. Using our rovibrational energies and recently measured excitation lines, we are able to improve the T_e values and dissociation energies of five excited states to an accuracv of ±8 cm^?1.     

The low-temperature (5 to 310 K) heat capacity and thermodynamic functions of cesium fluoroxysulfate (CsSO4F) and the standard potential at 298.15 K for the half-reaction: SO4F−(aq) + 2H+(aq) + 2e− = HSO4−(aq) + HF(aq)

The low-temperature (5 to 310 K) heat capacity of cesium fluoroxysulfate, CsSO₄F, has been measured by adiabatic calorimetry. At T = 298.15 K, the heat capacity C_p^o(T) and standard entropy S^o(T) are (163.46±0.82) and (201.89±1.01) J · K^?1 · mol^?1, respectively. Based on an earlier measurement of the standard enthalpy of formation ΔH_f^o the Gibbs energy of formation ΔG_f^o(CsSO₄F, c, 298.15 K) is calculated to be ?(877.6±1.6) kJ · mol^?1. For the half-reaction: SO₄F^?(aq)+2H⁺(aq)+2e^? = HSO₄^?(aq)+HF(aq), the standard electrode potential E at 298.15 K, is (2.47±0.01) V.     

Isotopic effect in the radiolysis of water. Diffusion-kinetic modelling up to 300°C

Diffusion-kinetic calculations [1-3] have been analysed to determine the isotopic effect in the radiolysis of water with ionising radiation of linear energy transfer characteristics (LET) from 0.2 to 60 eV/nm and at temperatures up to 300°C. This analysis shows that, for low LET radiation, the spur decay of e^- _aq is slower in D₂O and results in a higher yield of e^- _aq, g(e^- _aq), at 10^-7 -10^-6s after the ionisation event. In low LET radiolysis, g(OD) ≈ g(OH) over the whole range of temperature but in high LET radiolysis g(OD) is clearly lower than g(OH). The isotopic effect on the yields of the radical products is enhanced by increasing LET but diminished by increasing temperature. The yields of the molecular products show the opposite isotopic effect to their radical precursors, namely g(D₂) is 10-20% lower than g(H₂) and g(D₂O₂) > g(H₂O₂). A particularly significant difference between g(D₂O₂) and g(H₂O₂) has been found at LET = 20 eV/nm. The isotopic dependence of the g-values estimated for fast neutron radiolysis is also presented.     

Volume properties and structure of aqueous solutions of urea at 263–348 K

The apparent molar volume of urea ? in aqueous solution in the range T = 273–323 K and m = 1–10 (molality) depends linearly on m ^1/2. An equation for ?(m, T) was derived. The partial molar characteristics of urea ? ₂ and water ? ₁ (volume, dilatability, and temperature coefficients of volumes) were calculated. The ?(T) dependences have characteristic points (extrema, inflection points), shifted to the region of lower temperatures for dilute solutions. The ? ₁(T) dependences for 2m and 4m of the urea solution retain the characteristics of the Y ₁(T) of pure water. In these solutions, the proper structure of water is preserved.     

Evaluation of the stability of dye heteroassociates formed in aqueous solutions

The additive tetraphenylarsonium-tetraphenylborate model of interactions was found to be applicable to the problem of “preexperimental” evaluation of the stability of associates formed by dye cations (Ct⁺) and anions (An^?) in aqueous solutions. The possibility of predicting equilibrium association constants K _as from preliminarily calculated ΔG(Ct⁺) and ΔG(An^?) and of solving the inverse problem was analyzed. The invariability of the ΔG(Ct⁺) and ΔG(An^?) values and the problem of bringing calculation results in consistency with the experimental K _as values are discussed.     

B−B Bond Nucleophilicity in a Tetraaryl μ‐Hydridodiborane(4) Anion

The tetraaryl μ‐hydridodiborane(4) anion [ 2 H]^? possesses nucleophilic B?B and B?H bonds. Treatment of K[ 2 H] with the electrophilic 9‐H‐9‐borafluorene (HBFlu) furnishes the B₃ cluster K[ 3 ], with a triangular boron core linked through two BHB two‐electron, three‐center bonds and one electron‐precise B?B bond, reminiscent of the prominent [B₃H₈]^? anion. Upon heating or prolonged stirring at room temperature, K[ 3 ] rearranges to a slightly more stable isomer K[ 3 a ]. The reaction of M[ 2 H] (M⁺=Li⁺, K⁺) with MeI or Me₃SiCl leads to equimolar amounts of 9‐R‐9‐borafluorene and HBFlu (R=Me or Me₃Si). Thus, [ 2 H]^? behaves as a masked [:BFlu]^? nucleophile. The HBFlu by‐product was used in situ to establish a tandem substitution‐hydroboration reaction: a 1:1 mixture of M[ 2 H] and allyl bromide gave the 1,3‐propylene‐linked ditopic 9‐borafluorene 5 as sole product. M[ 2 H] also participates in unprecedented [4+1] cycloadditions with dienes to furnish dialkyl diaryl spiroborates, M[R₂BFlu].     

Negative ion chemical ionization mass spectrometry—binding of molecules to bromide and iodide anions

The analytical potential of negative ion chemical ionization (NICI) mass spectrometry utilizing dibromodifluoro-methane (CF₂Br₂) and iodomethane (CH₃I)/methane (CH₄) as reagent gases is examined. The NICI mass spectrum of CF₂Br₂ contains Br^?, [HBr₂]^? and [CF₂Br₃]^? anions. Weak acids (i.e. those acids with approximately ΔH°_(acid) values between 1674 and 1464 kJ mol^?1) react with Br^? to produce minor yields of the hydrogen?bonded bromide attachment [MH + Br]^? anion or are unreactive. Strong acids (i.e. those acids with approximately ΔH°_(acid) > 1464 kJ mol^?1) produce primarily [MH + Br]^? anions with a minor yield of proton transfer [M ? H]^? anion. The NICI spectrum of CH₃I/CH₄ is dominated by I^?. Weak acids react with I^? to yield minor amounts of [MH + 1]^? or are unreactive. Strong acids produce only [MH + l]^? anions. From a consideration of the gas-phase basicity of the halide anion and the binding energy of the hydrogen-bonded halide attachment adduct, thermochemical data are used as a potential guide to rationalize or predict the ions observed in NICI mass spectra.