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

Abstract

Cyclometalated platinum(II) complexes [Pt(ppy)Cl(CNAr)] (ppy = 2-phenylpyridinato-C 2 , N ; Ar = C 6 H 4 -2-I 1 , C 6 H 4 -4-I 2 , C 6 H 3 -2-F-4-I 3 , and C 6 H 3 -2,4-I 2 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 ·CHCl 3 , 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 ·CHCl 3 demonstrated a reversible mechanochromic color change achieved by mechanical grinding (green to orange) and solvent adsorption (orange to green).

Controlled Halogen-Bond-Involving Assembly of Double-σ-Hole-Donating Diaryliodonium Cations and Ditopic Arene Sulfonates

“…A similar methodology has been previously used for the studies of halogen bonded systems. 56,114,115 In some cases ([1] 2 (1,5-NDS), [2] 2 (2,6-NDS), and [1] 2 (2,6-NDS)_a), the starting fractional coordinates were shifted along one of the translation vectors by 0.5 to move the pairs of interacting atoms within one cell. These shifts do not change their mutual arrangements due to the existence of an inversion center in all cases.…”

“…However, to achieve 1.0 × 10 –6 hartree convergence for the self-consistent-field cycle in the Γ-point approximation, for [ 3 ] 2 (1,5-NDS) and [ 1 ] 2 (2,6-NDS)_b structures with large cell volumes (2337.13(8) and 3129.95(5) Å 3 , respectively), the SVP-MOLOPT-SR-GTH basis was applied for all C atoms, which are not bonded covalently to I or S atoms. A similar methodology has been previously used for the studies of halogen bonded systems. ,, In some cases ([ 1 ] 2 (1,5-NDS), [ 2 ] 2 (2,6-NDS), and [ 1 ] 2 (2,6-NDS)_a), the starting fractional coordinates were shifted along one of the translation vectors by 0.5 to move the pairs of interacting atoms within one cell. These shifts do not change their mutual arrangements due to the existence of an inversion center in all cases.…”

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

“…67 The packing mode of compounds 1Y-4Y seems to depend on the nature of the cyclometalating ligand and the Y atom (Table S6 ‡). In particular, chlorine-containing molecules 1Cl, 2Cl and 4Cl do not exhibit XB I⋯Cl that involve an iodine atom of IPy, in contrast to a known example, 25 and 3Cl is unique in the set that reflects in the electronic structure, vide infra. However, this is the only one regular correlation that can be detected from the experimental data.…”

“…The Pt(II) centre provides a convenient platform to obtain such complexes with dual functionality, and several examples have already been published. [23][24][25][26] However, this is insufficient for a systematic approach in the study of supramolecular assembly of dual functional complexes. It is also important to take into account that the Pt(II) atom can also act as a XB acceptor due to the interaction of the σ-hole of X with the d z 2 orbital of Pt(II).…”

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

“…Crystallization of 7 produced two crystalline forms: red crystals formed from a boiling CHCl 3 solution (denoted as 7 A ) and yellow crystals obtained via the slow evaporation of a CHCl 3 solution at RT (denoted as 7 B ). The yellow color is typical for nonaggregated C,N-cyclometalated Pt II complexes, while the red is specific for solid Pt II complexes featuring Pt···Pt metallophilic interactions . In the case of 6 , 8 , and 9 , only one type of crystal was obtained.…”