Flexibility of cubane-like Cu4I4 framework: temperature dependence of molecular structure and luminescence thermochromism of [Cu4I4(PPh3)4] in two polymorphic crystalline states

Kitagawa, Hakuba; Ozawa, Yoshiki; Toriumi, Koshiro

doi:10.1039/c0cc01434f

Cited by 152 publications

(147 citation statements)

References 22 publications

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“…One relevant parameter to account for the global variation of the six Cu−Cu distances in the clusters is the corresponding Cu 4 tetrahedron volume. 25 Thus, by comparing these values with those of the monoclinic polymorph (3P), 25 a similar behavior is observed when the sample is cooled with similar rate of shortening for very close values (Supporting Information, Figure S10). This means that in the case of 3, this shortening is not sufficient to induce changes in the energy of the T 1 state and consequently of the LE emission band.…”

Section: ■ Introductionsupporting

confidence: 71%

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Geometry Flexibility of Copper Iodide Clusters: Variability in Luminescence Thermochromism

Benito¹,

Goff²,

Nocton³

et al. 2015

Inorg. Chem.

142

144

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An original copper(I) iodide cluster of novel geometry obtained by using a diphosphine ligand is reported and is formulated [Cu6I6(PPh2(CH2)3PPh2)3] (1). Interestingly, this sort of "eared cubane" cluster based on the [Cu6I6] inorganic core can be viewed as a combination of the two known [Cu4I4] units, namely, the cubane and the open-chair isomeric geometries. The synthesis, structural and photophysical characterisations, as well as theoretical study of this copper iodide along with the derived cubane (3) and open-chair (2) [Cu4I4(PPh3)4] forms, were investigated. A new polymorph of the cubane [Cu4I4(PPh3)4] cluster is indeed presented (3). The structural differences of the clusters were analyzed by solid-state nuclear magnetic resonance spectroscopy. Luminescence properties of the three clusters were studied in detail as a function of the temperature showing reversible luminescence thermochromism for 1 with an intense orange emission at room temperature. This behavior presents different feature compared to the cubane cluster and completely contrasts with the open isomer, which is almost nonemissive at room temperature. Indeed, the thermochromism of 1 differs by a concomitant increase of the two emission bands by lowering the temperature, in contrast to an equilibrium phenomenon for 3. The luminescence properties of 2 are very different by exhibiting only one single band when cooled. To rationalize the different optical properties observed, density functional theory calculations were performed for the three clusters giving straightforward explanation for the different luminescence thermochromism observed, which is attributed to different contributions of the ligands to the molecular orbitals. Comparison of 3 with its [Cu4I4(PPh3)4] cubane polymorphs highlights the sensibility of the emission properties to the cuprophilic interactions.

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Section: ■ Introductionsupporting

confidence: 71%

“…47 This agrees with the cubic polymorph presenting even longer Cu−Cu distances and almost no shift. 25 Thus, for 3, only the relative population of the two excited states (T 1 and T 2 ) changes with the temperature leading to a perfectly controlled thermochromism with no band shifting.…”

Section: ■ Introductionmentioning

confidence: 98%

Geometry Flexibility of Copper Iodide Clusters: Variability in Luminescence Thermochromism

Benito¹,

Goff²,

Nocton³

et al. 2015

Inorg. Chem.

142

144

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“…The Cu−X and Cu−P bond distances in both Cu 2 X 2 -[O,O] complexes are close to those observed in the tetranuclear cubane-type clusters [Cu 4 (μ 3 -X) 4 (PPh 3 ) 4 ] (cCu 4 X 4 : X = Br − and I − ). 17,21 The bond distances between Cu(I) and the O atom of the DMSO ligand are independent of the halide ion. The notable differences between the two Cu 2 X 2 -[O,O] complexes are the Cu−X−Cu bond angles and Cu···Cu distance in the rhombic unit; the Cu···Cu distance in the rhombic {Cu 2 (μ-X) 2 } unit is well-known to exert a significant impact on the photophysical properties of Cu(I)−halide cluster complexes.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…19,22 Certain Cu(I) cluster complexes with phosphine ligands exhibit interesting thermochromic luminescence, which is thought to originate from switching of the emissive excited state from the triplet mixed halide-to-ligand and metal-to-ligand charge transfer (mixed 3 XLCT and 3 MLCT) state to the 3 CC state. 21 before and after removal of DMSO by heating at 423 K for 1 day. Prior to DMSO removal, both complexes exhibit bright blue luminescence (Φ em = 0.19 and 0.14, respectively) centered at 440 nm.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Photo- and Vapor-Controlled Luminescence of Rhombic Dicopper(I) Complexes Containing Dimethyl Sulfoxide

et al. 2013

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Halide-bridged rhombic dicopper(I) complexes, [Cu2(μ-X)2(DMSO)2(PPh3)2] (X = I(-), Br(-); DMSO = dimethyl sulfoxide; PPh3 = triphenylphosphine), were synthesized, the iodide complex of which exhibited interesting photochromic luminescence driven by photoirradiation and by exposure to DMSO vapor in the solid state. Single-crystal X-ray diffraction measurements revealed that the iodo and bromo complexes (abbreviated Cu2I2-[O,O] and Cu2Br2-[O,O]) were isomorphous, and that the two DMSO ligands were coordinated to the Cu(I) ion via the O atom in both complexes. Both complexes exhibited bright blue phosphorescence at room temperature (λ(em) = 435 nm, Φ(em) = 0.19 and 0.14 for Cu2I2-[O,O] and Cu2Br2-[O,O], respectively) with a relatively long emission lifetime (τ(em) ~ 200 μs at 77 K) derived from the mixed halide-to-ligand and metal-to-ligand charge transfer ((3)XLCT and (3)MLCT) excited state. Under UV irradiation, the blue phosphorescence of Cu2Br2-[O,O] disappeared uneventfully and no new emission band appeared, whereas the blue phosphorescence of Cu2I2-[O,O] rapidly disappeared with simultaneous appearance of a new green emission band (λ(em) = 500 nm). On further irradiation, the green emission of the iodide complex gradually changed to bright yellowish-green (λ(em) = 540 nm); however, this change could be completely suppressed by lowering the temperature to 263 K or in the presence of saturated DMSO vapor. The initial blue phosphorescence of Cu2I2-[O,O] was recovered by exposure to DMSO vapor at 90 °C for a few hours. IR spectroscopy and theoretical calculations suggest that the DMSO ligand underwent linkage isomerization from O-coordination to S-coordination, and both the occurrence of linkage isomerization and the removal of DMSO result in contraction of the rhombic Cu2(μ-I)2 core to make the Cu···Cu interaction more effective. In the contracted core, the triplet cluster-centered ((3)CC) emissive state is easily generated by thermal excitation of the (3)XLCT and (3)MLCT mixed transition state, resulting in the green to yellowish-green emission. In contrast, the Cu···Cu distance in Cu2Br2-[O,O] is considerably longer than that of Cu2I2-[O,O], which destabilizes the (3)CC emissive state, resulting in the nonemissive character.

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“…Such long distances, correlated with the steric effect of the ligands and/or to crystal packing, explain the lack of red shift of the LE band of 41 by lowering the temperature, contrarily to what observed for 39 having 2.90 Å Cu···Cu distances which becomes closer to the 2.8 Å value. M a n u s c r i p t Edited Mar 5 4 polymorphs by performing a multi-temperature X-ray crystal structure analysis [48]. [CuI(PPh 3 )] 4 was prepared by reaction of CuI with PPh 3 .…”

Section: Insert Chartmentioning

confidence: 99%

Cu(I) hybrid inorganic–organic materials with intriguing stimuli responsive and optoelectronic properties

Cariati

Lucenti

Botta

et al. 2016

Coordination Chemistry Reviews

370

264

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Flexibility of cubane-like Cu4I4 framework: temperature dependence of molecular structure and luminescence thermochromism of [Cu4I4(PPh3)4] in two polymorphic crystalline states

Abstract: Multitemperature X-ray structure analyses and photoemission spectra of [Cu(4)I(4)(PPh(3))(4)] in two polymorphic crystals reveal that the cubane-like framework is flexibly distorted effecting luminescence thermochromism.

Cited by 152 publications

References 22 publications

Geometry Flexibility of Copper Iodide Clusters: Variability in Luminescence Thermochromism

Geometry Flexibility of Copper Iodide Clusters: Variability in Luminescence Thermochromism

Photo- and Vapor-Controlled Luminescence of Rhombic Dicopper(I) Complexes Containing Dimethyl Sulfoxide

Cu(I) hybrid inorganic–organic materials with intriguing stimuli responsive and optoelectronic properties

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