Structure, Dynamics, and Photophysics in the Copper(I) Iodide–Tetrahydrothiophene System

Combination
of CuI and tetrahydrothiophene (THT) in MeCN or neat
THT produces various phases, depending upon experimental conditions.
Green luminescent product (CuI)4(THT)2 (1) consists of Cu4I4 cubane units knit
into a 3-D network by μ2-THT ligands. Dull yellow
luminescent (CuI)10(THT)7(MeCN) (2) contains {[Cu4I4(THT)]­(μ2-THT)2(Cu2I2)­(μ2-THT)2[Cu4I4(NCMe)]} “rungs”
linked into 1-D ladders by pairs of μ2-THT ligands.
Two molecular (CuI)4(THT)4 phases were found:
orange luminescent 3a and yellow luminescent 3b. Triclinic 3b is the more stable phase at 25 °C,
but it undergoes endothermic transformation to monoclinic 3a at 38 °C. Compound 3a transforms to a triclinic
phase (3a′) that retains orange emission at −60
°C. Nonemissive (CuI)3(THT)3·MeCN
(4) is a 2-D sheet structure in which Cu3(THT)3 rings are linked in trigonal directions by rhomboid Cu2I2 dimer units. The previously reported (CuI)2(THT)4 (5) is a molecular dimer. Temperature
and mixing ratio domains for the formation of the CuI–THT phases
from MeCN are presented. Luminescence in 1, 2, 3a, and 3b is rationalized on the basis
of varying degrees of halide-to-metal charge transfer (XMCT) and metal-centered
(MC) behavior. Low-temperature spectra reveal reversible changes,
including modest red shifts for 1 and 2,
and splitting into two excitation/emission band pairs for 3a and 3b.

在乙腈（MeCN）或纯四氢噻吩（tetrahydrothiophene, THT）中混合碘化亚铜（CuI）与四氢噻吩（THT），可根据实验条件得到不同晶相产物。发绿色光的产物(CuI)₄(THT)₂(1)由Cu₄I₄立方烷单元构成，这些单元通过μ₂桥联THT配体编织成三维网状结构。发暗黄色光的(CuI)₁₀(THT)₇(MeCN)(2)含有{[Cu₄I₄(THT)]-(μ₂-THT)₂(Cu₂I₂)-(μ₂-THT)₂[Cu₄I₄(NCMe)]}“梯级单元”，该单元通过成对的μ₂桥联THT配体连接成一维梯形链。现已得到两种(CuI)₄(THT)₄分子晶相：分别为发橙色光的3a与发黄光的3b。25 ℃下三斜晶系的3b为更稳定的晶相，但在38 ℃时会发生吸热相变，转变为单斜晶系的3a。化合物3a在-60 ℃时会转变为仍能发射橙色光的三斜晶相3a'。无发光特性的(CuI)₃(THT)₃·MeCN(4)呈现二维层状结构：其中Cu₃(THT)₃环通过菱形Cu₂I₂二聚体单元沿三角晶向相互连接。此前已有报道的(CuI)₂(THT)₄(5)为分子二聚体。本文还给出了在乙腈体系中由CuI与THT合成各晶相的温度与投料比范围。产物1、2、3a与3b的发光性能可通过不同程度的卤化物到金属电荷转移（XMCT）与金属中心（MC）电子跃迁行为进行合理解释。低温光谱测试显示体系存在可逆光谱变化：其中产物1与2的发射峰发生小幅红移，而3a与3b的激发/发射峰则分裂为两对双峰。