Rodgers M T, Armentrout P B
Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
J Am Chem Soc. 2002 Mar 20;124(11):2678-91. doi: 10.1021/ja011278+.
Threshold collision-induced dissociation of M(+)(adenine) with xenon is studied using guided ion beam mass spectrometry. M(+) includes all 10 first-row transition metal ions: Sc(+), Ti(+), V(+), Cr(+), Mn(+), Fe(+), Co(+), Ni(+), Cu(+), and Zn(+). For the systems involving the late metal ions, Cr(+) through Cu(+), the primary product corresponds to endothermic loss of the intact adenine molecule, whereas for Zn(+), this process occurs but to form Zn + adenine(+). For the complexes to the early metal ions, Sc(+), Ti(+), and V(+), intact ligand loss competes with endothermic elimination of purine and of HCN to form MNH(+) and M(+)(C(4)H(4)N(4)), respectively, as the primary ionic products. For Sc(+), loss of ammonia is also a prominent process at low energies. Several minor channels corresponding to formation of M(+)(C(x)H(x)N(x)), x = 1-3, are also observed for these three systems at elevated energies. The energy-dependent collision-induced dissociation cross sections for M(+)(adenine), where M(+) = V(+) through Zn(+), are modeled to yield thresholds that are directly related to 0 and 298 K bond dissociation energies for M(+)-adenine after accounting for the effects of multiple ion-molecule collisions, kinetic and internal energy distributions of the reactants, and dissociation lifetimes. The measured bond energies are compared to those previously studied for simple nitrogen donor ligands, NH(3) and pyrimidine, and to results for alkali metal cations bound to adenine. Trends in these results and theoretical calculations on Cu(+)(adenine) suggest distinct differences in the binding site propensities of adenine to the alkali vs transition metal ions, a consequence of s-dsigma hybridization on the latter.
使用导向离子束质谱法研究了M(+)(腺嘌呤)与氙的阈碰撞诱导解离。M(+)包括所有10种第一排过渡金属离子：Sc(+)、Ti(+)、V(+)、Cr(+)、Mn(+)、Fe(+)、Co(+)、Ni(+)、Cu(+)和Zn(+)。对于涉及晚期金属离子（从Cr(+)到Cu(+)）的体系，主要产物对应于完整腺嘌呤分子的吸热损失，而对于Zn(+)，这个过程也会发生，但会形成Zn + 腺嘌呤(+)。对于与早期金属离子（Sc(+)、Ti(+)和V(+)）形成的配合物，完整配体的损失与嘌呤和HCN的吸热消除相互竞争，分别形成MNH(+)和M(+)(C₄H₄N₄)作为主要离子产物。对于Sc(+)，在低能量下氨的损失也是一个显著过程。在较高能量下，对于这三个体系还观察到了几个对应于M(+)(CₓHₓNₓ)（x = 1 - 3）形成的次要通道。对M(+)(腺嘌呤)（其中M(+) = V(+)到Zn(+)）的能量相关碰撞诱导解离截面进行建模，以得出在考虑多离子 - 分子碰撞、反应物的动能和内能分布以及解离寿命的影响后，与M(+) - 腺嘌呤在0和298 K时的键解离能直接相关的阈值。将测得的键能与先前对简单氮供体配体NH₃和嘧啶的研究结果以及与腺嘌呤结合的碱金属阳离子的结果进行了比较。这些结果的趋势以及对Cu(+)(腺嘌呤)的理论计算表明，腺嘌呤与碱金属离子和过渡金属离子的结合位点倾向存在明显差异，这是后者上s - dσ杂化的结果。
