IRMPD spectroscopy of metalated flavins: structure and bonding of M(q+)-lumichrome complexes (M(q+) = Li⁺-Cs⁺, Ag⁺, Mg²⁺).
IRMPD spectroscopy of metalated flavins: structure and bonding of M(q+)-lumichrome complexes (M(q+) = Li⁺-Cs⁺, Ag⁺, Mg²⁺).
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DOI：
10.1039/c4cp01524j
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发表时间：
2014-06
期刊：
影响因子：
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通讯作者：
A. Günther;P. Nieto;G. Berden;J. Oomens;O. Dopfer
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文献类型：
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作者：
A. Günther;P. Nieto;G. Berden;J. Oomens;O. Dopfer
在指纹范围内记录质量选择的分离金属-发光铬离子络合物 M(q+)LCn（其中 M(q+) = Li(+)、Na(+)、K(+)、Rb(+)、Cs(+)、Ag(+) (n = 1) 和 Mg(2+) (n = 2)）的红外多光子解离 (IRMPD) 光谱。这些复合物是在与离子回旋加速器质谱仪和红外自由电子激光器 FELIX 连接的电喷雾电离源中产生的。 IMPD 光谱的振动和异构体分配是通过 B3LYP/cc-pVDZ 水平的密度泛函理论计算完成的，这可以深入了解复合物的结构、结合能、键合机制和光谱特性。确定的两个主要结合位点涉及与 LC 两个可用羰基（表示为 O2 和 O4）的氧原子的金属键合。更稳定的 O4 异构体得益于与 LC 附近 N5 原子的孤对电子的额外相互作用。虽然 M(+)LC 与碱金属主要通过静电力稳定，但 Ag(+)LC 配合物显示出部分共价贡献带来的额外稳定性。最后，双正电荷大大增强了 Mg(2+) 离子与 LC 的相互作用。 C[双键，长度为m-dash]O拉伸模式的频率是金属结合位点和金属键强度的敏感指标。
Infrared multiphoton dissociation (IRMPD) spectra of mass selected isolated metal-lumichrome ionic complexes, M(q+)LCn with M(q+) = Li(+), Na(+), K(+), Rb(+), Cs(+), Ag(+) (n = 1), and Mg(2+) (n = 2), are recorded in the fingerprint range. The complexes are generated in an electrospray ionization source coupled to an ion cyclotron mass spectrometer and the IR free electron laser FELIX. Vibrational and isomer assignments of the IRMPD spectra are accomplished by density functional theory calculations at the B3LYP/cc-pVDZ level, which provide insight into the structure, binding energy, bonding mechanism, and spectral properties of the complexes. The two major binding sites identified involve metal bonding to the oxygen atoms of the two available carbonyl groups of LC (denoted O2 and O4). The more stable O4 isomer benefits from an additional interaction with the lone pair of the nearby N5 atom of LC. While M(+)LC with alkali metals are mainly stabilized by electrostatic forces, the Ag(+)LC complex reveals additional stabilization arising from partly covalent contributions. Finally, the interaction of Mg(2+) ions with LC is largely enhanced by the doubled positive charge. The frequencies of the C[double bond, length as m-dash]O stretching modes are a sensitive indicator of both the metal binding site and the metal bond strength.