Halogen Bonding to Amplify Luminescence: A Case Study Using a Platinum Cyclometalated Complex

Chiral Canoe-Like Pd0 or Pt0 Alloyed Copper Alkynyl Nanoclusters Display Near-Infrared Luminescence

Alloying nanoclusters (NCs) has emerged as a widely explored and versatile strategy for tailoring tunable properties, facilitating in-depth atomic-level investigations of structure-property correlations. In this study, we have successfully synthesized six atomically precise copper NCs alloyed with Group 10 metals (Pd or Pt). Notably, the Pd0 or Pt0 atom situated at the center of the distorted hexagonal antiprism Pd0/Pt0@Cu12 cage, coordinated with twelve Cu+ and two tBuC≡C- ligands. Moreover, ligand exchange strategies demonstrated the potential for Cl- and Br- to replace one or two alkynyl ligands positioned at the top or side of the NCs. The chirality exhibited by these racemic NCs is primarily attributed to the involvement of halogens and a chiral (Pd/Pt)@Cu18 skeleton. Furthermore, all the NCs exhibit near-infrared (NIR) luminescence, characterized by emission peaks at 705-755 nm, lifetimes ranging from 6.630 to 9.662 μs, and absolute photoluminescence quantum yields (PLQYs) of 1.75 %-2.52 % in their crystalline state. The experimental optical properties of these NCs are found to be in excellent agreement with the results of theoretical calculations. These alloy NCs not only offer valuable insights into the synthesis of Pd0/Pt0-Cu alloy NCs, but also bridge the gap in understanding the structure-luminescence relationships of Pd0/Pt0-Cu molecules.

X/Y platinum(II) complexes: some features of supramolecular assembly via halogen bonding

Four series of new luminescent cyclometalated complexes [Pt(C^N)(IPy)Y] (HC^N = 2-phenylpyridine (Hppy), 2-(1-benzofuran-3-yl)pyridine (Hbfpy), methyl-2-phenylquinoline-4-carboxylate (Hmpqc), 2-(1-benzothiophen-3-yl)pyridine (Hbtpy), IPy = 4-iodopyridine, and Y = Cl, Br, I) have been investigated as X/Y 'building blocks' for the construction of a supramolecular network utilizing the I atom in IPy as a halogen bond (XB) donor (the X atom). The σ-hole of the X atom was found to provide non-covalent X⋯Y, X⋯Pt and X⋯π (π system of the metalated chelate ring) interactions for the complexes in the crystal state. NBO analysis confirms donation of the platinum electron density to iodine upon the X⋯Pt interaction. The nature of the X counterpart in XB depends on the nature of the Y atom and the cyclometalating ligand of the Pt(II) complex. DFT calculations show that the HOMO of [Pt(C^N)(IPy)Y] in the S0 state is delocalized over Pt, Y and a C-coordinating fragment of C^N, while the LUMO in most complexes is formed by the Py orbitals of IPy. However, the α-HOMO in the lowest triplet state of [Pt(C^N)(IPy)Y] contains no contribution of the IPy wavefunctions. All Pt(II) complexes exhibited triplet luminescence in solution and in the solid state (Φ up to 0.129), which is determined by the nature of the C^N ligand. The emission profile is independent of the nature of the ligand Y, while the quantum yield decreases from Cl to I. Accordingly, on the basis of DFT calculation, this emission is interpreted as a C^N intraligand charge transfer predominantly. The XB formation did not show an effect on the luminescence of the complexes in the solid phase, however grinding of crystals results in an increase of brightness.

Halogen Bond Induced Structural and Photophysical Properties Modification in Organic-Inorganic Hybrid Manganese Halides

The role of halogen bonding in organic-inorganic hybrid (OIH) halides was seldom investigated despite its potential to enhance the stability of the compound. In this context, we have synthesized (2-methylbenzimidazolium)MnCl₃(H₂O)·H₂O (compound 1) crystallizing in a monoclinic space group P2₁/c with a 1D infinite chain of edge shared Mn octahedra. In contrast, the chloro-substituted derivative (5-chloro-2-methylbenzimidazolium)₂MnCl₄ (compound 2) exhibits 0D Mn tetrahedra with a triclinic P1̅ structure. This structural modification from 1D Mn octahedra to 0D Mn tetrahedra involves a unique type-II halogen bonding between organic chlorine (C-Cl) and inorganic chloride (Cl-Mn) ions. Compound 1 exhibits red emission, whereas compound 2 demonstrates dual-band emission, resulting from energy transfer from the organic amine to Mn centers. To rationalize this interesting modulation in structure and photophysical properties, the role of halogen bonding is explored in terms of quantitative electron density analysis and intermolecular interaction energies.

(2-Hydroxy-3-Methoxybenzylidene)thiazolo[3,2-a]pyrimidines: Synthesis, Self-Assembly in the Crystalline Phase and Cytotoxic Activity

A series of new 2-hydroxy-3-methoxybenzylidenethiazolo[3,2-a]pyrimidines with different aryl substituents at the 5 position are synthesized and characterized by ¹H/ ¹³C NMR and IR-spectroscopy and mass-spectrometry, as well as single crystal X-ray diffraction (SCXRD). It was demonstrated that the type of hydrogen bonding can play a key role in the chiral discrimination of these compounds in the crystalline phase. The hydrogen bond of the O-H...N type leads to 1D supramolecular heterochiral chains or conglomerate crystallization in the case of the formation of homochiral chains. The hydrogen bond of O-H...O type gave racemic dimers, which are packed into 2D supramolecular layers with a parallel or angular dimers arrangement. Halogen bonding of the N...Br or O...Br type brings a new motif into supramolecular self-assembly in the crystalline phase: the formation of 1D supramolecular homochiral chains instead 2D supramolecular layers. The study of cytotoxicity against various tumor cells in vitro was carried out. It was found that 2-hydroxy-3-methoxybenzylidenethiazolo[3,2-a]pyrimidines with 3-nitrophenyl substituent at C5 carbon atom demonstrated a high efficiency against M-HeLa (cervical adenocarcinoma) and low cytotoxicity against normal liver cells.

The Halogen Bonding Proclivity of the sp3 Sulfur Atom as a Halogen Bond Acceptor in Cocrystals of Tetrahydro-4H-thiopyran-4-one and Its Derivatives

In this work, we present a systematic study of the capability of the sp³ hybridized sulfur atom for halogen bonding both in a small building block, tetrahydro-4H-thiopyran-4-one, and two larger ones derived from it, Schiff bases with a morpholine fragment on the other end of the molecule. These three building blocks were cocrystallized with six perhalogenated aromates: 1,4-diiodotetrafluorobenzene, 1,3,5-triiodotrifluorobenzene, 1,3-diiodotetrafluorobenzene, 1,2-diiodotetrafluorobenzene, iodopentafluorobenzene, and 1,4-dibromotetrafluorobenzene. Out of the 18 combinations, only 7 (39%) yielded cocrystals, although with a high occurrence of the targeted I···S halogen bonding motif in all cocrystals (71%), and in imine cocrystals the I···O_morpholine motif (100%) as well as, surprisingly, the I···N_imine motif (100%). The I···S halogen bonds presented in this work feature lower relative shortening values than those for other types of sulfur atoms; however, the sp³ sulfur atom could potentially be more specific an acceptor for halogen bonding.

Polymorph-Dependent Phosphorescence of Cyclometalated Platinum(II) Complexes and Its Relation to Non-covalent Interactions

Cyclometalated platinum(II) complexes [Pt(ppy)Cl(CNAr)] (ppy = 2-phenylpyridinato-C²,N; Ar = C₆H₄-2-I 1, C₆H₄-4-I 2, C₆H₃-2-F-4-I 3, and C₆H₃-2,4-I₂ 4) bearing ancillary isocyanide ligands were obtained by the bridge-splitting reaction between the dimer [Pt(ppy)(μ-Cl)]₂ and 2 equiv any one of the corresponding CNAr. Complex 2 was crystallized in two polymorphic forms, namely, 2 ^I and 2 ^II, exhibiting green (emission quantum yield of 0.5%) and orange (emission quantum yield of 12%) phosphorescence, respectively. Structure-directing non-covalent contacts in these polymorphs were verified by a combination of experimental (X-ray diffraction) and theoretical methods (NCIplot analysis, combined electron localization function (ELF), and Bader quantum theory of atoms in molecules (QTAIM analysis)). A noticeable difference in the spectrum of non-covalent interactions of 2 ^I and 2 ^II is seen in the Pt···Pt interactions in 2 ^II and absence of these metallophilic contacts in 2 ^I. The other solid luminophores, namely, 1, 3 ^I-II, 4, and 4·CHCl₃, exhibit green luminescence; their structures include intermolecular C-I···Cl-Pt halogen bonds as the structure-directing interactions. Crystals of 1, 2 ^I, 3 ^I, 3 ^II, 4, and 4·CHCl₃ demonstrated a reversible mechanochromic color change achieved by mechanical grinding (green to orange) and solvent adsorption (orange to green).

Halogen Bonding Involving Gold Nucleophiles in Different Oxidation States

A single-crystal X-ray diffraction (XRD) study of diaryliodonium tetrachloroaurates (or, in the recent terminology, tetrachloridoaurates), [(p-XC₆H₄)₂I][AuCl₄] (X = Cl, 1; Br, 2), was performed for 1 (the structure is denoted as 1a to show similarity with the isomorphic structure 2a) and two polymorphs─2a (obtained from MeOH) and 2b (from 1,2-C₂H₄Cl₂). Examination of the XRD data for these three structures revealed 2-center C-X···Au^III (X = Cl and Br) and 3-center bifurcated C-Br···(Cl-Au) halogen bonding (abbreviated as XB) between the p-Cl or p-Br atoms of the diaryliodonium cations and the gold(III) atom of [AuCl₄]^-. The noncovalent nature of Au^III-involving interactions, the nucleophilicity of the gold(III) atoms, and the electrophilic role of p-X atoms of the diaryliodonium cations in the XBs were studied by a set of complementary computational methods. Combined experimental and theoretical studies allowed the recognition of the d-nucleophilicity of the [d⁸Au^III] atom which, regardless of its rather substantial formal 3+ charge, can function as a d-nucleophilic partner of XB. This conclusion was also supported by theoretical calculations performed for the structures' refcodes BINXOM and ICSD 62511; the obtained data verified the nucleophilicity of Au^III toward a K⁺ ions or a σ-(Cl)-hole, respectively. All our results, together with consideration of relevant literature, indicate that gold atoms in the three oxidation states (0, I, and even III) exhibit nucleophilicity in XBs.

Chameleonic Metal-bound Isocyanides: π-Donating CuI-center Imparts a Nucleophilicity to the Isocyanide Carbon toward Halogen Bonding

In the structures of the isostructural cocrystals [CuI3(CNXyl)3]·CHX3 (X = Br, I), two adjacent CuI-bound isocyanide groups, whose carbon lone pairs are blocked by the ligation, exhibit nucleophilic properties induced...

Helical donor-acceptor platinum complexes displaying dual luminescence and near-infrared circularly polarized luminescence

A series of chiral platina[5]helicenes displaying dual luminescence, i.e., fluorescence between 450 and 600 nm and red/NIR phosphorescence between 700 and 900 nm, has been synthesised, characterised and studied by first-principle calculations. This unusual behavior has been attributed to limited electronic interactions between the d orbitals of the metal and the π-orbitals of the organic ligand on the excited-state. Accordingly, the electron richness of the donor group on the helical ligand does not affect the energy of the phosphorescence process but does play a role on its efficiency. Interestingly, near-infrared circularly polarized luminescence can be obtained for the three complexes with dissymmetry factors up to 3 × 10^-3 at 750 nm.

Studies of Nature of Uncommon Bifurcated I-I···(I-M) Metal-Involving Noncovalent Interaction in Palladium(II) and Platinum(II) Isocyanide Cocrystals

Two isostructural trans-[MI2(CNXyl)2]·I2 (M = Pd or Pt; CNXyl = 2,6-dimethylphenyl isocyanide) metallopolymeric cocrystals containing uncommon bifurcated iodine···(metal-iodide) contact were obtained. In addition to classical halogen bonding, single-crystal X-ray diffraction analysis revealed a rare type of metal-involved stabilizing contact in both cocrystals. The nature of the noncovalent contact was studied computationally (via DFT, electrostatic surface potential, electron localization function, quantum theory of atoms in molecules, and noncovalent interactions plot methods). Studies confirmed that the I···I halogen bond is the strongest noncovalent interaction in the systems, followed by weaker I···M interaction. The electrophilic and nucleophilic nature of atoms participating in I···M interaction was studied with ED/ESP minima analysis. In trans-[PtI2(CNXyl)2]·I2 cocrystal, Pt atoms act as weak nucleophiles in I···Pt interaction. In the case of trans-[PdI2(CNXyl)2]·I2 cocrystal, electrophilic/nucleophilic roles of Pd and I are not clear, and thus the quasimetallophilic nature of the I···Pd interaction was suggested.

The Isocyanide Complexes cis-[MCl2(CNC6H4-4-X)2] (M = Pd, Pt; X = Cl, Br) as Tectons in Crystal Engineering Involving Halogen Bonds

The isocyanide complexes cis-[MCl2(CNC6H4-4-X)2] (M = Pd; X = Cl, Br; M = Pt; X = Br) form isomorphous crystal structures exhibiting the Cl/Br and Pd/Pt exchanges featuring 1D chains upon crystallisation. Crystal packing is supported by the C–X···X–C halogen bonds (HaBs), C–H···X–C hydrogen bonds (HB), X···M semicoordination, and C···C contacts between the C atoms of aryl isocyanide ligands. The results of DFT calculations and topological analysis indicate that all the above contact types belong to attractive noncovalent interactions. A projection of the electron localization function (ELF) and an inspection of the electron density (ED) and the electrostatic potential (ESP) reveal the amphiphilic nature of X atoms playing the role of HaB donors, HaB and HB acceptors, and a nucleophilic partner in X···M semicoordination.

Zn(II) Heteroleptic Halide Complexes with 2-Halopyridines: Features of Halogen Bonding in Solid State

Reactions between Zn(II) dihalides and 2-halogen-substituted pyridines 2-XPy result in a series of heteroleptic molecular complexes [(2-XPy)₂ZnY₂] (Y = Cl, X = Cl (1), Br (2), I (3); Y = Br, X = Cl (4), Br (5), I (6), Y = I, X = Cl (7), Br (8), and I (9)). Moreover, 1-7 are isostructural (triclinic), while 8 and 9 are monoclinic. In all cases, halogen bonding plays an important role in formation of crystal packing. Moreover, 1-9 demonstrate luminescence in asolid state; for the best emitting complexes, quantum yield (QY) exceeds 21%.

Modulation of Metallophilic and π-π Interactions in Platinum Cyclometalated Luminophores with Halogen Bonding

Luminescent cyclometalated complexes [M(C^N^N)CN] (M=Pt, Pd; HC^N^N=pyridinyl- (M=Pt 1, Pd 5), benzyltriazolyl- (M=Pt 2), indazolyl- (M=Pt 3, Pd 6), pyrazolyl-phenylpyridine (M=Pt 4)) decorated with cyanide ligand, have been explored as nucleophilic building blocks for the construction of halogen-bonded (XB) adducts using IC₆ F₅ as an XB donor. The negative electrostatic potential of the CN group afforded CN⋅⋅⋅I noncovalent interactions for platinum complexes 1-3; the energies of XB contacts are comparable to those of metallophilic bonding according to QTAIM analysis. Embedding the chromophore units into XB adducts 1-3⋅⋅⋅IC₆ F₅ has little effect on the charge distribution, but strongly affects Pt⋅⋅⋅Pt bonding and π-stacking, which lead to excited states of MMLCT (metal-metal-to-ligand charge transfer) origin. The energies of these states and the photoemissive properties of the crystalline materials are primarily determined by the degree of aggregation of the luminophores via metal-metal interactions. The adduct formation depends on the nature of the metal and the structure of the metalated ligand, the variation of which can yield dynamic XB-supported systems, exemplified by thermally regulated transition 3↔3⋅⋅⋅IC₆ F₅ .

A series of luminescent Cu(i) complexes based on the diphosphine ligand and diimine ligand: weak intermolecular interactions, terahertz spectroscopy and photoproperties

Counter-ions can regulate the luminescence of complexes by changing the weak intermolecular interactions, which can be observed by THz spectroscopy.

Modulation of luminescence properties for [cyclometalated]-PtII(isocyanide) complexes upon co-crystallisation with halosubstituted perfluorinated arenes

C–X⋯Cl–Pt Halogen bonds and πh⋯d_z2[Pt^II] contacts led to the 2-fold increase of phosphorescence quantum yields for [cyclometalated]-Pt^II(isocyanide) complexes upon co-crystallisation with halosubstituted perfluorinated arenes.

Crystal engineering strategies towards halogen-bonded metal–organic multi-component solids: salts, cocrystals and salt cocrystals

This highlight presents an overview of the current advances in the preparation of halogen bonded metal–organic multi-component solids, including salts and cocrystals comprising neutral and ionic constituents.

Molecular and Polymer Ln2M2 (Ln = Eu, Gd, Tb, Dy; M = Zn, Cd) Complexes with Pentafluorobenzoate Anions: The Role of Temperature and Stacking Effects in the Structure; Magnetic and Luminescent Properties

Varying the temperature of the reaction of [{Cd(pfb)(H2O)4}+n·n(pfb)-], [Ln2(pfb)6(H2O)8]·H2O (Hpfb = pentafluorobenzoic acid), and 1,10-phenanthroline (phen) in MeCN followed by crystallization resulted in the isolation of two type of products: 1D-polymers [LnCd(pfb)5(phen)]n·1.5nMeCN (Ln = Eu (I), Gd (II), Tb (III), Dy (IV)) which were isolated at 25 °C, and molecular compounds [Tb2Cd2(pfb)10(phen)2] (V) formed at 75 °C. The transition from a molecular to a polymer structure becomes possible because of intra- and intermolecular interactions between the aromatic cycles of phen and pfb from neighboring tetranuclear Ln2Cd2 fragments. Replacement of cadmium with zinc in the reaction resulted in molecular compounds Ln2Zn2 [Ln2Zn2(pfb)10(phen)2]·4MeCN (Ln = Eu (VI), Tb (VIII), Dy (IX)) and [Gd2Zn2(pfb)10(H2O)2(phen)2]·4MeCN (VII). A new molecular EuCd complex [Eu2Cd2(pfb)10(phen)4]·4MeCN (X)] was isolated from a mixture of cadmium, zinc, and europium pentafluorobenzoates (Cd:Zn:Ln = 1:1:2). Complexes II-IV, VII and IX exhibit magnetic relaxation at liquid helium temperatures in nonzero magnetic fields. Luminescent studies revealed a bright luminescence of complexes with europium(III) and terbium(III) ions.

π-Hole···dz2[PtII] Interactions with Electron-Deficient Arenes Enhance the Phosphorescence of PtII-Based Luminophores

Two phosphorescent Pt^II-based cyclometalated complexes were co-crystallized with perfluorinated arenes to give 1:1 co-crystals. The X-ray study revealed that each of the complexes is embraced by arenes^F to give infinite reverse sandwich structures. In four out of six structures, a d_z² orbital of Pt^II is directed to the arenes^F ring via π-hole···d_z²[Pt^II] interactions, whereas in the other two structures, the filled d_z² orbital is directed toward the arene C atoms. Computed molecular electrostatic potential surfaces of the arenes^F and the complexes, noncovalent interaction indexes for the co-crystals, and natural bond orbital calculations indicate that π-hole···d_z²[Pt^II] contacts (and, generally, the stacking) are of electrostatic origin. The solid-state photophysical study revealed up to 3.5-fold luminescence quantum yield and 15-fold lifetime enhancements in the co-crystals. This increase is associated with the strength of the π-hole···d_z²[Pt^II] contact that is dependent on the π-acidity of the arene^F and its spatial characteristics.

Halogen Bonding in Isostructural Co(II) Complexes with 2-Halopyridines

Three complexes [Co(2-XPy)2Cl2] (X = Cl, Br, and I) were prepared and characterized, representing a rare case of isostructurality within the Cl-Br-I row. The nature of halogen bonding (XB) in a solid state was studied by DFT calculations, revealing a tendency of XB energy growth for heavier halogens.

Halogen Bonding Provides Heterooctameric Supramolecular Aggregation of Diaryliodonium Thiocyanate

The crystal structure of the newly synthesized 4-methoxyphenyl(phenyl)iodonium thiocyanate, [PhI(4-C6H4OMe)](SCN), represents the first example of 16-membered cyclic heterooctamer formed by halogen bonding between the iodonium cation and SCN−. Results of density functional theory (DFT) calculations followed by the topological analysis of the electron density distribution within the framework of the quantum theory of atoms in molecules (QTAIM) method at the ωB97XD/DZP-DKH level of theory reveal that energies of attractive intermolecular noncovalent interactions I···S and I···N (responsible for the formation of heterooctameric supramolecular clusters {PhI(4-C6H4OMe)}4·{SCN}4 in the solid state structure of [PhI(4-C6H4OMe)](SCN)) vary from 0.9 to 8.5 kcal/mol.

Terahertz time-domain absorption spectra of Cu(i) complexes bearing tetraphosphine ligands: the bridge between the C–H⋯π and π⋯π interactions and photoluminescence properties

The terahertz spectrum bridges the luminescence and C–H⋯π and π⋯π interactions of Cu(i) complexes.

The synthesis of cyclometalated platinum(II) complexes with benzoaryl-pyridines as C^N ligands for investigating their photophysical, electrochemical and electroluminescent properties

A series of (C^N)Pt(acac)-type complexes has been successfully synthesized with a benzo[b]furan, benzo[b]thiophene, benzo[b]selenophene, or benzo[b]tellurophene group in the benzoaryl-pyridine ligand. Using X-ray crystallography, the chemical structures of the complexes with benzo[b]selenophene and benzo[b]tellurophene groups have been clearly revealed. The photophysical, electrochemical, and electroluminescent (EL) behaviors of these (C^N)Pt(acac)-type complexes have been fully characterized. Furthermore, both time-dependent functional theory (TD-DFT) and natural transition orbital (NTO) theoretical results have been obtained to gain insight into the absorption and emission features. It has been shown that both the absorption bands with the lowest energy and the phosphorescence emission behaviors are dominated by the benzoaryl-pyridine cyclometalating ligand. Importantly, the effects of the group VIA atoms on the properties of these (C^N)Pt(acac)-type complexes have been revealed. Owing to the rareness of (C^N)Pt(acac)-type complexes with benzo[b]selenophene and benzo[b]tellurophene groups, their EL abilities have been characterized using solution-processed organic light-emitting diodes (OLEDs). The optimized red OLEDs with the complex bearing a benzo[b]selenophene unit show a maximum external quantum efficiency (ηext) of 6.3%, current efficiency (ηL) of 10.5 cd A-1, and power efficiency (ηP) of 9.1 lm W-1, while the EL device with the complex bearing a benzo[b]tellurophene unit can give deep-red emission at ca. 636 nm with ηext of 6.3%, ηL of 6.5 cd A-1, and ηP of 5.8 lm W-1. This research not only provides novel (C^N)Pt(acac)-type complexes, but also furnishes critical information regarding the photophysical and EL behavior of these new complexes.

Existence of untypical halogen-involving interactions in crystal packings: a statistical and first-principles study

There is a common perception by the scientific community that a halogen-involving interaction forms when the distance between the donor atom and the acceptor atom is less than the sum of their van der Waals (vdW) radii.

Tetrachloroplatinate(ii) anion as a square-planar tecton for crystal engineering involving halogen bonding

The tetrachloroplatinate(ii) anion behaves as a useful XB-accepting tecton toward sigma-hole-donating organohalide species.

Chlorotellurate(iv) supramolecular associates with “trapped” Br2: features of non-covalent halogen⋯halogen interactions in crystalline phases

Reactions of chlorotellurates(iv) and Br₂ afford formation of supramolecular complexes Cat₂{[TeCl₆](Br₂)} (Cat = Me₃N⁺ (1), PyH⁺ (2), 4-MePyH⁺ (3) and 1-MePy⁺ (4)) where dibromine fragments are “trapped” by [TeCl₆]³⁻via Br⋯Cl halogen bonding.

Highly Efficient Deep-Red Organic Light-Emitting Devices Based on Asymmetric Iridium(III) Complexes with the Thianthrene 5,5,10,10-Tetraoxide Moiety

Highly efficient deep-red organic light-emitting devices (OLEDs) are indispensable for developing high-performance red-green-blue (RGB) displays and white OLEDs (WOLEDs). However, the shortage of deep-red emitters with high photoluminescence quantum yields (PLQYs) and balanced charge injection/transport abilities has severely restricted the performance of deep-red OLEDs. Herein, we design and synthesize four efficient emitters by combining the isoquinoline group with the thianthrene 5,5,10,10-tetraoxide group. Benefited from the introduction of the thianthrene 5,5,10,10-tetraoxide group, these Ir(III) complexes show improved electron-injection/-transport abilities. By enhancing the contribution of the triplet metal-to-ligand charge transfer (³MLCT) in emissions, the asymmetric configuration endows the related deep-red Ir(III) complexes with high PLQYs of 0.45-0.50 in solutions. More importantly, PLQYs of these Ir(III) complexes in doped host films increase up to 0.91, which is much higher than PLQYs reported for conventional deep-red Ir(III) complexes with impressive electroluminescent performance. As a result, solution-processed OLEDs based on these Ir(III) complexes exhibit deep-red emissions with Commission Internationale de L'Eclairage (CIE x, y) coordinates very close to the National Television System Committee (NTSC)-recommended standard red CIE coordinates of (0.67, 0.33). Furthermore, a deep-red OLED using the asymmetric Ir(III) complex SOIrOPh as the emitter shows outstanding performance with a peak external quantum efficiency (EQE) of 25.8%, which is the highest EQE reported for solution-processed deep-red OLEDs. This work sheds light on the great potential of utilizing the thianthrene 5,5,10,10-tetraoxide group to develop phosphorescent emitters for highly efficient OLEDs.

Extended Assemblies of Ru(bpy)(CO)2X2 (X = Cl, Br, I) Molecules Linked by 1,4-Diiodotetrafluoro-Benzene (DITFB) Halogen Bond Donors

The ruthenium carbonyl compounds, Ru(bpy)(CO)2X2 (X = Cl, Br or I) act as neutral halogen bond (XB) acceptors when co-crystallized with 1,4-diiodotetrafluoro-benzene (DITFB). The halogen bonding strength of the Ru-X⋅⋅⋅I halogen bonds follow the nucleophilic character of the halido ligand. The strongest halogen bond occurs between the chlorido ligand and the iodide atoms of the DITFB. All three halogen bonded complexes form polymeric assemblies in the solid state. In Ru(bpy)(CO)2Cl2⋅DITFB (1) and in Ru(bpy)(CO)2Br2⋅DITFB (2) both halido ligands are halogen bonded to only one DITFB donor. In Ru(bpy)(CO)2I2⋅DITFB (3) only one of the halido ligands is involved in halogen bonding acting as ditopic center for two DITFB donors. The polymeric structures of 1 and 2 are isomorphic wave-like single chain systems, while the iodine complexes form pairs of linear chains attached together with weak F⋅⋅⋅O≡C interactions between the closest neighbors. The stronger polarization of the iodide ligand compared to the Cl or Br ligands favors nearly linear C-I⋅⋅⋅I angles between the XB donor and the metal complex supporting the linear arrangement of the halogen bonded chain.

Blue-emitting bolaamphiphilic zwitterionic iridium(iii) complex

Aggregation induced emission is a very interesting phenomenon that recently has attracted a lot of interest. Most of the examples deal with organic molecules or flat metal complexes. Here we demonstrate that, by design, even iridium compounds can display this process without shifting the emission energy. In order to enhance the aggregation properties we have focussed on amphiphilic complexes. We report the synthesis and photophysical characterisation of a blue-emitting bolaamphiphilic zwitterionic Ir(iii) complex and an analogous cationic amphiphilic compound, used as a reference. The bolaamphiphile exhibited blue (λmax = 450 nm) emission in dilute, deaerated solution with a photoluminescence quantum yield (PLQY) of 22%, similar to the related cationic amphiphilic complex. The bolaamphiphile displayed significant emission enhancement in the solid state, with an emission quantum yield that reach 52%. Interestingly, the emission of the cationic analogue suffers from aggregation quenching in the solid state, (PLQY = 3%) as is common for these type of complexes. A correlation between the photophysical data and the arrangement in the solid state is discussed.

Aggregation-enhanced emissive mechanofluorochromic carbazole-halogen positional isomers: tunable fluorescence via conformational polymorphism and crystallization-induced fluorescence switching

The conformational twist of the carbazole-halogen positional isomers produced blue and green polymorphs with tunable solid-state fluorescence and demonstrated mechanofluorochromism.

Recognition of the π-hole donor ability of iodopentafluorobenzene – a conventional σ-hole donor for crystal engineering involving halogen bonding

This study is the first recognition of iodopentafluorobenzene's π-hole donor ability.

Tuning the solid-state emission by co-crystallization through σ- and π-hole directed intermolecular interactions

σ- and π-hole directed intermolecular interaction driven tuning of luminescence.

Halogen bonding in the structures of pentaiodobenzoic acid and its salts

Structural characterization of pentaiodobenzoic acid (PIBA) and its salts was performed for the first time.