Designing Magnetic Superalkalis with Extremely Large Nonlinear Optical Responses

Predicting superatoms with multiple desired properties
is of great
interest and challenge. To achieve this goal, a series of organometallic
M@36adz (M = Sc ∼ Zn) complexes have been obtained
by embedding the 3d transition-metal atoms into the 36adamanzane
(36adz) complexant. Under the intramolecular interaction
between M and 36adz, the magnetic moments of M atoms are
either enhanced or preserved in the resulting M@36adz complexes.
Also, the αSOMO levels of M@36adz
are significantly raised by the presence of the M impurities, resulting
in their greatly lower adiabatic ionization energies (AIEs) of 1.78–2.56
eV than the IE (3.89 eV) of Cs atom. As a result, these complexes
can be regarded as a new kind of magnetic superalkalis. Moreover,
due to the existence of diffuse electrons in their αSOMO, most of the M@36adz complexes also exhibit remarkable
nonlinear optical responses with large first hyperpolarizabilities
(β0) of 1.56 × 106–6.33 ×
107 au. Hence, this study provides a possible strategy
to design a new kind of multifunctional species with high reducing
ability, magnetic properties, and large NLO responses by doping various
transition metals into such cage-like organic complexants.

精准预测具备多种期望属性的超原子（superatoms），是兼具重要研究价值与挑战性的课题。为达成这一目标，本研究通过将3d过渡金属原子嵌入至36-金刚烷（36adamanzane，36adz）配体中，成功合成了一系列有机金属型M@36adz（M = Sc ∼ Zn）配合物。在金属M与36adz的分子内相互作用下，所得M@36adz配合物中金属原子的磁矩得以增强或保持稳定。此外，金属M的掺入显著提升了M@36adz的α单占据分子轨道（αSOMO）能级，使得其绝热电离能（adiabatic ionization energy, AIE）仅为1.78~2.56 eV，远低于铯（Cs）原子的电离能（ionization energy, IE，3.89 eV）。据此，这类配合物可被视为一类新型磁性超碱金属。此外，由于其αSOMO轨道中存在弥散电子，多数M@36adz配合物还展现出优异的非线性光学（nonlinear optical, NLO）响应，其第一超极化率（first hyperpolarizability, β0）可达1.56×10^6~6.33×10^7 原子单位（atomic units, au）。综上，本研究提出了一种可行的设计策略：通过将各类过渡金属掺杂至这类笼状有机配体中，可制备兼具高还原能力、磁学特性与优异非线性光学响应的新型多功能物种。