Skip to main content
NCBI home page
ACS AuthorChoice logoLink to ACS AuthorChoice
. 2024 Mar 12;63(12):5315–5319. doi: 10.1021/acs.inorgchem.3c03346

Phosphorescent Cyclometalated Palladium(II) and Platinum(II) Complexes Derived from Diaminocarbene Precursors

Maria V Kashina †, Konstantin V Luzyanin ‡,*, Dmitry V Dar’in †, Stanislav I Bezzubov §, Mikhail A Kinzhalov †,*
PMCID: PMC10966732  PMID: 38470336

Abstract

graphic file with name ic3c03346_0007.jpg

Metal-mediated self-assembly of isocyanides and methyl 4-aminopyrimidine-5-carboxylate leads to luminescent PdII and PtII complexes featuring C,N-cyclometalated acyclic diaminocarbene (ADC) ligands. The solid-state luminescent properties of these diaminocarbene derivatives are attributed to their triplet-state metal/metal-to-ligand charge-transfer (3MMLCT) nature, which is driven by attractive intermolecular M···M interactions further reinforced by the intramolecular π–π interactions even in the structure of the Pd compound, which is the first Pd-ADC phosphor reported.

Short abstract

Unique examples of Pd and Pt acyclic diaminocarbene complexes showing room-temperature aggregation-induced phosphorescence are given.

Driven by their remarkable potential as organic light-emitting diodes,1,2 in bioimaging,3,4 photocatalysis,5 and optical chemosensing,6 luminescent complexes of transition metals have attracted significant research interest. Tuning the photoemission of metal complexes requires the judicious selection of ligands, with cyclometalated aromatic species currently dominating the field for several compelling reasons.1 The introduction of secondary σ-donor ligands of strong ligand field, i.e., N-heterocyclic carbenes (NHCs) or acyclic diaminocarbenes (ADCs), increases the quantum efficiency and brings up the possibility of the precise tuning of emission profiles.7 Recent studies described cyclometalated complexes of PtII and IrIII featuring ancillary NHC- and ADC-containing ligands (Figure 1A).

Figure 1.

Figure 1

Open in a new tab

(A) Representative PtII and IrIII complexes with diaminocarbenes.8−10 (B) Examples of PdII complexes displaying aggregation-induced phosphorescent emission.11,12

Whereas PtII and IrIII luminescent derivatives are more explored, their PdII counterparts remain scarce, which is primarily attributed to weaker ligand-field splitting compared to that of the 5d metals arising from the less diffuse 4d orbitals of PdII. Among rare examples of luminescent PdII species (Figure 1B),11−13 ligands of strong field and highly rigid coordination environments are prerequisites to sustain their luminescence at room temperature (RT). ADCs stand out as unique ancillary ligands showcased by a broad range of applications, and luminescent ADC complexes of IrIII, PtII, ReI, and AuI/III have been described.7

Unsurprisingly, although Pd-ADC species are widely used in transition-metal catalysis,14,15 to the best of our knowledge, none of them have been shown as phosphorescent (an example of a fluorescent complex has recently been reported16). In the present report, we reveal the preparation of a unique example of phosphorescent cyclometalated PdII-ADC complexes alongside their respective PtII-ADC species and elucidate their luminescent properties.

The synthetic route to new ADC complexes involves the reaction between isocyanide 1 or 2 with methyl 4-aminopyrimidine-5-carboxylate (3) in CHCl3 at RT (20–25 °C), leading to C,N-cyclometalated diaminocarbene derivatives 4 and 5 (Scheme 1, Route A). Under CHCl3 reflux conditions, 4 and 5 spontaneously deprotonate to the respective 6 and 7 (Route B), which were isolated in 77–79% yield. The reaction of 6 or 7 with another 1 equiv of 3 in the presence of 1,1,3,3-tetramethylguanidine as a base furnishes bis(C,N-cyclometalated) deprotonated diaminocarbene complexes 8 and 9 (Route C, 88–95% isolated yields).

Scheme 1. Preparation of 4–9.

Scheme 1

Open in a new tab

Structural elucidation for 5–9, isolated as air-stable pale-yellow to orange solids, was aided by CHN microanalyses, high-resolution positive-ion electrospray ionization mass spectromety, IR, ultraviolet/visible (UV/vis), and NMR spectroscopy, and single-crystal X-ray diffraction (XRD) for 5–9. A partial conversion of 4 into 6 was observed upon evaporation of the solution; therefore, 4 was characterized only in the CDCl3 solution. A full description of the experimental procedures including the characterization of all compounds thus prepared can be found in the Supporting Information (SI).

Crystallization of 7 produced two crystalline forms: red crystals formed from a boiling CHCl3 solution (denoted as 7A) and yellow crystals obtained via the slow evaporation of a CHCl3 solution at RT (denoted as 7B). The yellow color is typical for nonaggregated C,N-cyclometalated PtII complexes, while the red is specific for solid PtII complexes featuring Pt···Pt metallophilic interactions.17 In the case of 6, 8, and 9, only one type of crystal was obtained. The PdII/PtII metal center adopts a distorted planar-square coordination geometry completed with one (6 and 7) or two (9 and 10) C,N-cyclometalated diaminocarbene ligands (Figure 2). The C–N bond distances in the diaminocarbene moiety are between typical single and double CN bonds, denoting a significant electron density delocalization in this fragment.

Figure 2.

Figure 2

Open in a new tab

Structures of 6 (left) and 8 (right) with displacement ellipsoids at the 50% level. Crystal structures of 7B and 9 are similar to those of 6 and 8, respectively, and their views are given in the SI along with relevant crystal data.

The UV/vis spectra of 5–9 in CH2Cl2 display high-energy intense absorption bands at 250–300 nm assigned to the transitions to ligand-centered states (π–π*), together with less intense bands at 300–400 nm (Figure S5). From the data on related complexes featuring cyclometalated diaminocarbene ligands,18 these bands can be associated with the transitions to mixed singlet-state ligand-to-ligand charge-transfer (1LL′CT) and singlet-state intraligand charge-transfer (1ILCT) states. It cannot, however, be ruled out that the weak band at 406 nm for the bis(cyclometalated) PtII complex is due to the direct S1 → T1 transition enabled by the large spin–orbit coupling of the Pt center. Such bands are typically not observed for the PdII counterparts due to a reduced spin–orbit coupling constant of Pd compared to Pt. Solid-state absorption spectra are different from the absorption spectra in solution; viz., they allowed low-energy bands in the spectra for 5, 7A, 8, and 9 to be observed (Figure S7). The low-energy bands make PtII complex 9 look orange in color to the human eye due to transitions to metal/metal-to-ligand charge-transfer (MMLCT) states. The UV/vis spectra of 7 in the 0.03–1.2 mM concentration range were obtained (Figure S6). The shape of the UV/vis absorption spectra for the red form 7 is not influenced by the concentration within the range of 0.03–1.2 mM, and no bands after 400 nm that can be attributed to the MMLCT states are observed. This indicates that any possible aggregation has little to no impact on the ground-state behavior in the solution. UV/vis measurements of 8 and 9 with more than 0.03 mM concentration were not possible due to the low solubility of these compounds.

The deoxygenated CH2Cl2 solutions of 4–9 displayed negligible luminescence at RT. Upon photoexcitation at RT, crystalline 5, 7A, 8, and 9 exhibited intense luminescence, with different colors ranging from green (8) to red (9) (Figure 3), while the PdII complexes 4 and 6 and PtII compound 7B were not emissive. All luminescent complexes show a large Stokes shift and lifetimes in the microsecond domain that clearly indicate the triplet character (phosphorescence) of the emissive state.

Figure 3.

Figure 3

Open in a new tab

Normalized excitation (dotted lines) and emission (solid lines) spectra of 5, 7A, 8, and 9 in the solid state at RT. The insets show photographs of the complexes obtained under 365 nm UV irradiation.

The nonstructured emission suggests that the excited state has a large metal orbital participation due to the formation of weak metal–metal-connected aggregates in the ground state or excimers in the excited state.19 This agrees with the short M···M contacts identified in 8 and 9. For solid 8 and 9 featuring comparable metal–metal distances in their crystal structure, a red shift on going from Pd to Pt indicates an enhanced d-orbital coupling (4dz2 vs 5dz2). All crystals 5, 7A, 8, and 9 show monoexponential decay with radiative rate constants (kr) as high as 105 s–1. These high values of kr support a triplet-state metal/metal-to-ligand charge-transfer (3MMLCT)-based parentage for the emitting excited state in 5, 7A, 8, and 9, which is substantially larger than the kr value of ligand-centered excited states with typical values on the order of 103 s–1.2 Grinding crystals 8 and 9 in an agate mortar induces no observable effect on their photoluminescence (Figure S14).

A phenomenon observed when a nonemissive species is induced to emit by formation of aggregates is referred to as aggregation-induced emission.20 Noteworthily, very few examples of PdII complexes that showed RT aggregation-induced phosphorescent emission have been reported so far (Figures 1B and S18).11,12,21−25 Strassert et al. described PdII complexes featuring tetradentate ligands,12 while Lu et al. reported pincer PdII allenylidene derivatives.8 Although the aforementioned reports support the role of self-assembly as an enabler of phosphorescence, the extent to which solid-state phosphorescence can be generated rationally upon chemical structure analysis is compulsive for further investigation.

In poly(methyl methacrylate) (PMMA) films, the spectrum of 8 demonstrates emission identical with that recorded in the solid state, while the spectra of PtII species 7 and 9 exhibit additional blue-shifted bands resembling the emission of a nonaggregated complex (Figures S8–S12). The emission lifetime measured for this band showed a biexponential τobs, with one long-lifetime component being appreciably different from that of the main peak (Table S8). This behavior is assignable to the coexistence of both 3MMLCT and 3MLCT states. Thus, the lack of emission in solution for the PtII complexes is due to the conformational flexibility of cyclohexyl substituents, which can serve as a relaxation channel for the excited states via a nonradiative decay to the ground state.20 In the case of the PdII compounds, the emission of nonaggregated complexes is absent due to the population of nonradiative metal-centered states.12

In crystal format, compounds 8 and 9 self-organize in a head-to-tail manner, producing supramolecular dimers (Figure 4). The distances between the metal atoms in (8)2 and (9)2 [3.2312(3)–3.3379(5) Å] are comparable to the sum of Bondi’s vdW radii (0.94–1.02) but smaller than the sum of Alvarez’s (0.71–0.78) van der Waals (vdW) radii, indicating the possibility of metallophilic Pd···Pd and Pt···Pt interactions. In an attempt to understand the nature of M···M interactions, we utilized density functional theory calculations, Bader’s quantum theory of atoms-in-molecules26 together with a noncovalent interaction index plot27,28 (QTAIM/NCIplot), and analysis of the electron localization function (ELF).29−31

Figure 4.

Figure 4

Open in a new tab

Hirshfeld surfaces for 8. Dimeric supramolecular architecture of 8 resulting from M···M interaction (purple dotted lines), C···N (blue dotted lines), and C···O (red dotted lines) contacts. The Hirshfeld surface for 9 is similar, and its view is given in the SI.

QTAIM analysis of the computed (8)2 and (9)2 reveals that the M···M interactions are depicted by the bond critical points (BCPs) and bond paths linking the metal centers; apart from the M···M interaction, the BCPs for additional interactions (namely, C···N and C···O contacts) stabilizing the (8)2 and (9)2 assembly (Figure 5) were found. By a comparison of the QTAIM values of ρ(r) at the BCPs, it can be concluded that M···M is a structure-directing interaction for these supramolecular assemblies. Only a low density of ρ = 0.014–0.023 was determined, reflected in the low Mayer/Wiberg bond orders32 (0.16/0.18 for 8 and 0.44/0.24 for 9) and ultimately with a weakly bonding interaction.

Figure 5.

Figure 5

Open in a new tab

QTAIM distribution of BCPs and bond paths for the clusters (8)2 (top) and (9)2 (bottom). Only BCPs and NCIplot surfaces characterizing intermolecular interactions are represented for clarity. The insets show ELF projections for the M···M interactions in (8)2 and (9)2.

The increased ELF areas around the PdII and PtII atoms near the bond paths connecting metal centers can be interpreted as filled dz2 orbitals. Low ELF values between the intermetal regions indicate the absence of covalent character of these interactions. In both cases, the 1D profiles of the electron density and electrostatic potential functions33 along the M···M bond paths overlap (Figure S15). This confirms the nonpolar noncovalent nature of M···M interactions similar to that observed recently for other systems with metallophilic interactions.17,34 Based on the experimental and theoretical findings, the Pd···Pd and Pt···Pt interactions in 8 and 9 are of an intramolecular d8–d8 metallophilic nature.

In summary, we have reported a high-yielding synthesis of a series of PdII and PtII cyclometalated complexes featuring deprotonated ADCs. The strong ligand field and rigid chelate system of C,N-cyclometalated diaminocarbenes induces solid-state luminescence for Pt and bis(diaminocarbene) Pd derivatives ranging from the green to red spectral region. The emission is attributed to a long-lived triplet-manifold excited state with MMLCT character associated with the formation of attractive M···M interactions. These preliminary photophysical results show that the rational design of acyclic C,N-cyclometalated diaminocarbene-based ligands provides access to unique luminescent PdII derivatives. The emergence of intermolecular interactions is recognized as a driving force toward the phosphorescence of diaminocarbene complexes described in this work, and our future efforts will be dedicated to a better understanding of the relationship between the molecular construction and luminescence properties of metal aminocarbene species.

Acknowledgments

This paper is dedicated to the commemoration of the 300th anniversary of the founding of St. Petersburg State University. Analytical and photophysical measurements were undertaken using the facilities of the Center for Magnetic Resonance, the Center for X-ray Diffraction Studies, the Center for Chemical Analysis and Materials Research, the Center for Optical and Laser Materials Research, the Center for Diagnostics of Functional Materials for Medicine, Pharmacology and Nanoelectronics, the Thermogravimetric and Calorimetric Research Centre, the Computing Centre, and the Cryogenic Department (all at the St. Petersburg State University).

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.inorgchem.3c03346.

  • Experimental section, spectral, XRD, and experimental data, structural features discussion, and theoretical calculations (PDF)

Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

This work was supported by the Russian Science Foundation (Project 21-73-10083).

The authors declare no competing financial interest.

Supplementary Material

ic3c03346_si_001.pdf (3.8MB, pdf)

References

  1. Chi Y.; Chou P.-T. Transition-metal phosphors with cyclometalating ligands: fundamentals and applications. Chem. Soc. Rev. 2010, 39 (2), 638–655. 10.1039/B916237B. [DOI] [PubMed] [Google Scholar]
  2. To W. P.; Wan Q. Y.; Tong G. S. M.; Che C. M. Recent Advances in Metal Triplet Emitters with d(6), d(8), and d(10) Electronic Configurations. Trends Chem. 2020, 2 (9), 796–812. 10.1016/j.trechm.2020.06.004. [DOI] [Google Scholar]
  3. Holden L.; Burke C. S.; Cullinane D.; Keyes T. E. Strategies to promote permeation and vectorization, and reduce cytotoxicity of metal complex luminophores for bioimaging and intracellular sensing. RSC chem. biol. 2021, 2, 1021–1049. 10.1039/D1CB00049G. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Zhen X.; Qu R.; Chen W. Z.; Wu W.; Jiang X. Q. The development of phosphorescent probes for in vitro and in vivo bioimaging. Biomater. Sci. 2021, 9 (2), 285–300. 10.1039/D0BM00819B. [DOI] [PubMed] [Google Scholar]
  5. Twilton J.; Le C.; Zhang P.; Shaw M. H.; Evans R. W.; MacMillan D. W. C. The merger of transition metal and photocatalysis. Nat. Rev. Chem. 2017, 1 (7), 0052. 10.1038/s41570-017-0052. [DOI] [Google Scholar]
  6. Ma D.-L.; Wong S.-Y.; Kang T.-S.; Ng H.-P.; Han Q.-B.; Leung C.-H. Iridium(III)-based chemosensors for the detection of metal ions. Methods 2019, 168, 3–17. 10.1016/j.ymeth.2019.02.013. [DOI] [PubMed] [Google Scholar]
  7. Kinzhalov M. A.; Grachova E. V.; Luzyanin K. V. Tuning the Luminescence of Transition Metal Complexes with Acyclic Diaminocarbene Ligands. Inorg. Chem. Front. 2022, 9, 417–439. 10.1039/D1QI01288F. [DOI] [Google Scholar]
  8. Zou T.; Lok C.-N.; Fung Y. M. E.; Che C.-M. Luminescent organoplatinum(II) complexes containing bis(N-heterocyclic carbene) ligands selectively target the endoplasmic reticulum and induce potent photo-toxicity. Chem. Commun. 2013, 49 (47), 5423–5425. 10.1039/c3cc40953h. [DOI] [PubMed] [Google Scholar]
  9. Li T.-Y.; Liang X.; Zhou L.; Wu C.; Zhang S.; Liu X.; Lu G.-Z.; Xue L.-S.; Zheng Y.-X.; Zuo J.-L. N-Heterocyclic Carbenes: Versatile Second Cyclometalated Ligands for Neutral Iridium(III) Heteroleptic Complexes. Inorg. Chem. 2015, 54 (1), 161–173. 10.1021/ic501949h. [DOI] [PubMed] [Google Scholar]
  10. Na H.; Teets T. S. Highly Luminescent Cyclometalated Iridium Complexes Generated by Nucleophilic Addition to Coordinated Isocyanides. J. Am. Chem. Soc. 2018, 140 (20), 6353–6360. 10.1021/jacs.8b02416. [DOI] [PubMed] [Google Scholar]
  11. Zou C.; Lin J.; Suo S.; Xie M.; Chang X.; Lu W. Palladium(II) N-heterocyclic allenylidene complexes with extended intercationic Pd···Pd interactions and MMLCT phosphorescence. Chem. Commun. 2018, 54 (42), 5319–5322. 10.1039/C8CC01652F. [DOI] [PubMed] [Google Scholar]
  12. Theiss T.; Buss S.; Maisuls I.; López-Arteaga R.; Brünink D.; Kösters J.; Hepp A.; Doltsinis N. L.; Weiss E. A.; Strassert C. A. Room-Temperature Phosphorescence from Pd(II) and Pt(II) Complexes as Supramolecular Luminophores: The Role of Self-Assembly, Metal–Metal Interactions, Spin–Orbit Coupling, and Ligand-Field Splitting. J. Am. Chem. Soc. 2023, 145 (7), 3937–3951. 10.1021/jacs.2c09775. [DOI] [PubMed] [Google Scholar]
  13. Lin J.; Zou C.; Zhang X.; Gao Q.; Suo S.; Zhuo Q.; Chang X.; Xie M.; Lu W. Highly phosphorescent organopalladium(II) complexes with metal–metal-to-ligand charge-transfer excited states in fluid solutions. Dalton Trans. 2019, 48 (28), 10417–10421. 10.1039/C9DT02525A. [DOI] [PubMed] [Google Scholar]
  14. Kinzhalov M. A.; Luzyanin K. V.. Enabling Catalytic Applications of Aminocarbene Ligands through Rational Design. In Synthesis and Applications in Chemistry and Materials; Pombeiro A. J. L., Guedes da Silva M. F. C., Mahmudov K., Eds.; Vol. 13: Metal Complex Catalytic Systems and Materials; World Scientific Publishing Co Pte Ltd, 2024; pp 3−44. https://www.worldscientific.com/doi/10.1142/9789811283222_0024. [Google Scholar]
  15. Kinzhalov M. A.; Luzyanin K. V. Synthesis and Contemporary Applications of Platinum Group Metals Complexes with Acyclic Diaminocarbene Ligands (A Review). Russ. J. Inorg. Chem. 2022, 67, 48–90. 10.1134/S0036023622010065. [DOI] [Google Scholar]
  16. Boyarskaya D. V.; Bulatov E.; Boyarskaya I. A.; Chulkova T. G.; Rassadin V. A.; Tolstopjatova E. G.; Kolesnikov I. E.; Avdontceva M. S.; Panikorovskii T. L.; Suslonov V. V.; Haukka M. Syntheses and Structures of a Series of Acyclic Diaminocarbene Palladium(II) Complexes Derived from 3,4-Diaryl-1H-pyrrol-2,5-diimines and Bisisocyanide Palladium(II) Complexes. Organometallics 2019, 38 (2), 300–309. 10.1021/acs.organomet.8b00725. [DOI] [Google Scholar]
  17. Sokolova E. V.; Kinzhalov M. A.; Smirnov A. S.; Cheranyova A. M.; Ivanov D. M.; Kukushkin V. Y.; Bokach N. A. Polymorph-Dependent Phosphorescence of Cyclometalated Platinum(II) Complexes and Its Relation to Non-covalent Interactions. ACS Omega 2022, 7 (38), 34454–34462. 10.1021/acsomega.2c04110. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Kashina M. V.; Luzyanin K. V.; Katlenok E. A.; Novikov A. S.; Kinzhalov M. A. Experimental and computational tuning of metalla-N-heterocyclic carbenes at palladium(II) and platinum(II) centers. Dalton Trans. 2022, 51 (17), 6718–6734. 10.1039/D2DT00252C. [DOI] [PubMed] [Google Scholar]
  19. Puttock E. V.; Walden M. T.; Williams J. A. G. The luminescence properties of multinuclear platinum complexes. Coord. Chem. Rev. 2018, 367, 127–162. 10.1016/j.ccr.2018.04.003. [DOI] [Google Scholar]
  20. Mei J.; Hong Y.; Lam J. W. Y.; Qin A.; Tang Y.; Tang B. Z. Aggregation-Induced Emission: The Whole Is More Brilliant than the Parts. Adv. Mater. 2014, 26 (31), 5429–5479. 10.1002/adma.201401356. [DOI] [PubMed] [Google Scholar]
  21. von der Stück R.; Krause M.; Brünink D.; Buss S.; Doltsinis N. L.; Strassert C. A.; Klein A. Luminescent Pd(II) Complexes with Tridentate – Aryl-pyridine-(benzo)thiazole Ligands. Z. Anorg. Allg. Chem. 2022, 648 (1), e202100278 10.1002/zaac.202100278. [DOI] [Google Scholar]
  22. Gutierrez Suburu M. E.; Maisuls I.; Kösters J.; Strassert C. A. Room-temperature luminescence from Pd(II) and Pt(II) complexes: from mechanochromic crystals to flexible polymer matrices. Dalton Trans. 2022, 51 (35), 13342–13350. 10.1039/D2DT01693A. [DOI] [PubMed] [Google Scholar]
  23. Gangadharappa S. C.; Maisuls I.; Gutierrez Suburu M. E.; Strassert C. A. Enhanced phosphorescence of Pd(II) and Pt(II) complexes adsorbed onto Laponite for optical sensing of triplet molecular dioxygen in water. Z. Naturforsch., B: J. Chem. 2021, 76 (10–12), 811–818. 10.1515/znb-2021-0136. [DOI] [Google Scholar]
  24. Hung F. F.; Wu S. X.; To W. P.; Kwong W. L.; Guan X. G.; Lu W.; Low K. H.; Che C. M. Palladium(II) Acetylide Complexes with Pincer-Type Ligands: Photophysical Properties, Intermolecular Interactions, and Photo-cytotoxicity. Chem. Asian J. 2017, 12 (1), 145–158. 10.1002/asia.201601414. [DOI] [PubMed] [Google Scholar]
  25. Akaiwa M.; Kanbara T.; Fukumoto H.; Yamamoto T. Luminescent palladium complexes containing thioamide-based SCS pincer ligands. J. Organomet. Chem. 2005, 690 (18), 4192–4196. 10.1016/j.jorganchem.2005.06.026. [DOI] [Google Scholar]
  26. Bader R. F. W. A quantum theory of molecular structure and its applications. Chem. Rev. 1991, 91 (5), 893–928. 10.1021/cr00005a013. [DOI] [Google Scholar]
  27. Contreras-García J.; Johnson E. R.; Keinan S.; Chaudret R.; Piquemal J.-P.; Beratan D. N.; Yang W. NCIPLOT: A Program for Plotting Noncovalent Interaction Regions. J. Chem. Theory Comput. 2011, 7 (3), 625–632. 10.1021/ct100641a. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Lefebvre C.; Rubez G.; Khartabil H.; Boisson J.-C.; Contreras-García J.; Hénon E. Accurately extracting the signature of intermolecular interactions present in the NCI plot of the reduced density gradient versus electron density. Phys. Chem. Chem. Phys. 2017, 19 (27), 17928–17936. 10.1039/C7CP02110K. [DOI] [PubMed] [Google Scholar]
  29. Becke A. D.; Edgecombe K. E. A simple measure of electron localization in atomic and molecular systems. J. Phys. Chem. 1990, 92 (9), 5397–5403. 10.1063/1.458517. [DOI] [Google Scholar]
  30. Silvi B.; Savin A. Classification of chemical bonds based on topological analysis of electron localization functions. Nature 1994, 371 (6499), 683–686. 10.1038/371683a0. [DOI] [Google Scholar]
  31. Savin A.; Nesper R.; Wengert S.; Fässler T. F. ELF: The Electron Localization Function. Angew. Chem., Int. Ed. 1997, 36 (17), 1808–1832. 10.1002/anie.199718081. [DOI] [Google Scholar]
  32. Bridgeman A. J.; Cavigliasso G.; Ireland L. R.; Rothery J. The Mayer bond order as a tool in inorganic chemistry. Dalton Trans. 2001, 14, 2095–2108. 10.1039/b102094n. [DOI] [Google Scholar]
  33. Bartashevich E.; Yushina I.; Kropotina K.; Muhitdinova S.; Tsirelson V. Testing the tools for revealing and characterizing the iodine-iodine halogen bond in crystals. Acta Crystallogr. B 2017, 73 (2), 217–226. 10.1107/S2052520617002931. [DOI] [PubMed] [Google Scholar]
  34. Bulatova M.; Ivanov D. M.; Rautiainen J. M.; Kinzhalov M. A.; Truong K.-N.; Lahtinen M.; Haukka M. Studies of Nature of Uncommon Bifurcated I–I···(I–M) Metal-Involving Noncovalent Interaction in Palladium(II) and Platinum(II) Isocyanide Cocrystals. Inorg. Chem. 2021, 60 (17), 13200–13211. 10.1021/acs.inorgchem.1c01591. [DOI] [PMC free article] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

ic3c03346_si_001.pdf (3.8MB, pdf)

Articles from Inorganic Chemistry are provided here courtesy of American Chemical Society

RESOURCES