Manganese(I) Complex with Monodentate Arylisocyanide Ligands Shows Photodissociation Instead of Luminescence

Ossinger, Sascha; Prescimone, Alessandro; Häußinger, Daniel; Wenger, Oliver S.

doi:10.1021/acs.inorgchem.2c01438

Cited by 7 publications

(29 citation statements)

References 191 publications

(422 reference statements)

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“…In comparison to [Mn-(CNdippPh OMe2 ) 6 ]PF 6 , the Re−C bond distances are slightly longer, consistent with a first row versus third row transition metal. 28 The C−Re−C bond angles ranging from 178.3(3) to 179.5(3)°and 88.5(2) to 91.5(3)°suggest that the complex has slightly distorted octahedral symmetry (see below). Similarly, this Mn(I) complex adopts a slightly distorted octahedral geometry.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Recently, a hexakisarylisocyanide Mn(I) complex, [Mn(CNdippPh OMe2 ) 6 ]PF 6 (CNdippPh OMe2 = 4-(3,5-dimethoxyphenyl)-2,6-diisopropyl-phenylisocyanide), was synthesized through a similar approach�reacting phenylisocyanide with Mn(CO) 5 Br followed by salt metathesis in an aqueous hexafluorophosphate solution. 28 The 1 H NMR spectrum of [Re(CNAr) 6 ]PF 6 shows 6 equivalent isocyanide ligands�a single resonance (δ ppm 2.46) is observed for the methyl substituents on the aryl ring and a doublet and doubletof-doublets are observed for the meta (H meta , δ ppm 7. X-ray diffraction quality crystals were grown via vapor diffusion of diethyl ether into a solution of the Re(I) complex in 1,2-difluorobenzene at −35 °C (Figure 1).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Similarly, this Mn(I) complex adopts a slightly distorted octahedral geometry. 28 Selected bond angles and distances are included in Table 1 (full crystallographic details are included in the Supporting Information). Though the hexakis Re(I) complex reported here has not been previously crystallized, the bond lengths of the equatorial CNAr ligands in Re(CNAr) 5 Cl are similar to those quantified for the hexakis complex.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The Mn(I) complex [Mn-(CNdippPh OMe2 ) 6 ]PF 6 exhibits a similar shift upon coordination from 2116 cm −1 for free ligand to 2070 cm −1 . 28 The manganese congener [Mn(CNPh) 6 ] + has a single isocyanide stretch at ν(C�N) = 2080 cm −1 . 8 For further comparison, studies of Re(CNR) 5 Cl report a single IR-active isocyanide stretch at lower energy ν(C�N) at 2044 cm −1 .…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…22 In addition to the strong stretch observed at 2065 cm −1 for [Re(CNAr) 6 ] + , a weak lower energy shoulder is observed at 2004 cm −1 , which has been reported for several [Mn(CNR) 6 ] + complexes. 8,28,29 Deviation from linearity of the C−N−R bond that results from π-backing and changes in hybridization at the N atom lowers the symmetry, leading to this shoulder. 28,29 The C−N−Ar bond angles of [Re(CNAr) 6 ] + are not perfectly linear [163.9(6) to 172.8( 7)°] and therefore correlate with this interpretation.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Isocyanide Ligands Promote Ligand-to-Metal Charge Transfer Excited States in a Rhenium(II) Complex

et al. 2023

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A metal-to-ligand charge transfer with mixed intraligand character is observed for the rhenium hexakisarylisocyanide complex [Re(CNAr)6]PF6 (CNAr = 2,6-dimethylphenylisocyanide, λmax = 300 nm). Upon oxidation to [Re(CNAr)6](PF6)2, the dominant low energy optical transition is a ligand-to-metal charge transfer (LMCT) mixed with intraligand transitions (λmax = 650 nm). TD-DFT was used to identify the participating ligand-based orbitals in the LMCT transition, revealing that the majority of the donor orbital is based on the aryl ring (85%) as opposed to the CN bond (14%). For both [Re(CNAr)6]+ and [Re(CNAr)6]2+, structural characterization by X-ray diffraction reveals deviations from Oh geometry at the central Re ion, with larger reduction in symmetry observed for Re(II). For [Re(CNAr)6]+, these structural changes lead to a broadening of the strong ν(CN) stretch (2065 cm–1), as the degeneracy of the T1u IR-active mode is broken. Furthermore, a shoulder is observed for this ν(CN) stretch, resulting from deviation of the C–N–Ar bond from linearity. By contrast, [Re(CNAr)6]2+ has two weak bands in the ν(CN) region (2065 and 2121 cm–1). DFT calculations indicate that reduction of symmetry at the central rhenium ion manifests in the decrease in intensity and the observed split of the ν(CN) band. Stability of both complexes are limited by light-induced decomposition where Re(I) dissociates a isocyanide ligand upon irradiation and Re(II) absorbance decays under ambient light. These data provide new insights to the electronic structure of [Re(CNAr)6]2+, enhancing our understanding of LMCT excited states and the versatility of isocyanide ligands.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

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Isocyanide Ligands Promote Ligand-to-Metal Charge Transfer Excited States in a Rhenium(II) Complex

et al. 2023

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The Nephelauxetic Effect Becomes an Important Design Factor for Photoactive First‐Row Transition Metal Complexes

2023

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The expansion of d‐orbitals as a result of metal‐ligand bond covalence, the so‐called nephelauxetic effect, is a well‐established concept of coordination chemistry, yet its importance for the design of new photoactive complexes based on first‐row transition metals is only beginning to be recognized. Until recently, much focus has been on optimizing the ligand field strength, coordination geometries, and molecular rigidity, but now it becomes evident that the nephelauxetic effect can be a game changer regarding the photophysical properties of 3d metal complexes in solution at room temperature. In CrIII and MnIV complexes with the d3 valence electron configuration, the nephelauxetic effect was exploited to shift the well‐known ruby‐like red luminescence to the near‐infrared spectral region. In FeII and CoIII complexes with the low‐spin d6 electron configuration, charge‐transfer excited states were stabilized with respect to detrimental metal‐centered excited states, to improve their properties and to enhance their application potential. In isoelectronic (3d6) isocyanide complexes of Cr0 and MnI, the nephelauxetic effect is likely at play as well, enabling luminescence and other favorable photoreactivity. This minireview illustrates the broad applicability of the nephelauxetic effect in tailoring the photophysical and photochemical properties of new coordination compounds made from abundant first‐row transition metals.

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First‐Row d⁶ Metal Complex Enables Photon Upconversion and Initiates Blue Light‐Dependent Polymerization with Red Light

Wang,

Wegeberg,

Wenger

2023

Angewandte Chemie

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Photosensitizers for sensitized triplet‐triplet annihilation upconversion (sTTA‐UC) often rely on precious heavy metals, whereas coordination complexes based on abundant first‐row transition metals are less common. This is mainly because long‐lived triplet excited states are more difficult to obtain for 3d metals, particularly when the d‐subshell is only partially filled. Here, we report the first example of sTTA‐UC based on a 3d6 metal photosensitizer yielding an upconversion performance competitive with precious metal‐based analogues. Using a newly developed Cr(0) photosensitizer featuring equally good photophysical properties as an Os(II) benchmark complex in combination with an acetylene‐decorated anthracene annihilator, red‐to‐blue upconversion is achievable. The upconversion efficiency under optimized conditions is 1.8%, and the excitation power density threshold to reach the strong annihilation limit is 5.9 W/cm2. These performance factors, along with high photostability, permit the initiation of acrylamide polymerization by red light, based on radiative energy transfer between delayed annihilator fluorescence and a blue light absorbing photo‐initiator. Our study provides the proof‐of‐concept for photon upconversion with elusive first‐row analogues of widely employed precious d6 metal photosensitizers, and for their application in photochemical reactions triggered by excitation wavelengths close to near‐infrared.

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Manganese(I) Complex with Monodentate Arylisocyanide Ligands Shows Photodissociation Instead of Luminescence

Cited by 7 publications

References 191 publications

Isocyanide Ligands Promote Ligand-to-Metal Charge Transfer Excited States in a Rhenium(II) Complex

Isocyanide Ligands Promote Ligand-to-Metal Charge Transfer Excited States in a Rhenium(II) Complex

The Nephelauxetic Effect Becomes an Important Design Factor for Photoactive First‐Row Transition Metal Complexes

First‐Row d⁶ Metal Complex Enables Photon Upconversion and Initiates Blue Light‐Dependent Polymerization with Red Light

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Manganese(I) Complex with Monodentate Arylisocyanide Ligands Shows Photodissociation Instead of Luminescence

Cited by 7 publications

References 191 publications

Isocyanide Ligands Promote Ligand-to-Metal Charge Transfer Excited States in a Rhenium(II) Complex

Isocyanide Ligands Promote Ligand-to-Metal Charge Transfer Excited States in a Rhenium(II) Complex

The Nephelauxetic Effect Becomes an Important Design Factor for Photoactive First‐Row Transition Metal Complexes

First‐Row d6 Metal Complex Enables Photon Upconversion and Initiates Blue Light‐Dependent Polymerization with Red Light

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First‐Row d⁶ Metal Complex Enables Photon Upconversion and Initiates Blue Light‐Dependent Polymerization with Red Light