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The synthesis of novel highly phosphorescent N^C^N tridentate platinum(II)-complex-peptide nucleic acid (PNA) bioconjugates was accomplished through the solid-phase approach. Melting temperature measurements and circular dichroism spectroscopy studies demonstrated that these conjugates maintain the PNA ability to recognize complementary ssDNA and ssRNA, though the length of the spacer between the metal center and the PNA sequence affects their hybridization properties. Noteworthy, the conjugation of PNA to this family of Pt(II) complexes significantly enhanced the luminescent features of the organometallic moiety, leading to increased quantum yields (82.8%, 10–5 M), even in the presence of oxygen (48.6%, 10–5 M). An in vitro cytotoxicity study of Pt(II)-PNA conjugates on HeLa cells showed no significative effect on cell growth in the dark (1 μM for 72 h). [ABSTRACT FROM AUTHOR]

Reaction of 4‐methylphenylacetylide with the known chlorido platinum(II) complex bearing the cyclometalated 1,3‐bis(pyridin‐2‐yl)‐4,6‐difluoro‐benzene ligand afforded a novel alkynyl platinum(II) complex, 1, that was fully characterized by elemental analysis, NMR and UV‐visible spectroscopies, by photoluminescence measurements, and by computational modelling. Its structure was determined by X‐ray diffraction studies on a single crystal whereas its second‐order nonlinear optical (NLO) properties were determined in solution by the Electric‐Field Induced Second Harmonic generation method. The novel multifunctional complex 1 is characterized by good luminescence properties, like the related chlorido Pt(II) complex, but by a much higher second‐order NLO response. [ABSTRACT FROM AUTHOR]

Materials based on small molecules characterized by multi‐component short and long‐lived emissive behaviour are extremely desirable for various applications. The derivative of cyclic triimidazole (TT) functionalized with a carboxylic group, namely TT‐COOH, is isolated, investigated and used as coordinative ligand to obtain a series of isomorphous mononuclear complexes of general formula [M(TT‐COO)2(H2O)2] (M=Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)). Crystals of TT‐COOH display aggregation induced enhanced emission (AIEE) comprising dual fluorescence and dual phosphorescence of molecular origin together with an aggregation induced long lived, low energy phosphorescence. Emissive features are retained in crystals of the Zn(II) and Cd(II) complexes, where the metal plays the role of an external heavy atom perturber, but strongly quenched in the others. The mechanisms involved in the photophysics of TT‐COOH and its metal complexes have been disclosed thanks to combined structural, spectroscopic and computational investigations which reveal the presence of anti‐Kasha emissions. [ABSTRACT FROM AUTHOR]

The versatility of a nitrogen rich pyridinic derivative of the cyclic triimidazole scaffold with C3 symmetry is here exploited to obtain three luminescent coordination polymers (CPs). By reaction of 3,7,11‐tri(pyridin‐4‐yl)triimidazo[1,2‐a:1′,2′‐c:1′′,2′′‐e][1,3,5]triazine, (4 py)3TT, with Ag(I), Cd(II) and Cu(I) salts, [Ag{(4‐py)3TT}(SO3CF3)]n ⋅ 1/2 ${{ 1/2 }}$ nCH2Cl2, [Cd{(4‐py)3TT}(NO3)2(EtOH)]n and [(Cu2I2)3{(4‐py)3TT}4]n ⋅ xn(H2O,EtOH) are obtained. The trigonal symmetry of (4 py)3TT results in 2D structures with hcb topology in [Ag{(4‐py)3TT}(SO3CF3)]n ⋅ 1/2 ${{ 1/2 }}$ nCH2Cl2 and [Cd{(4‐py)3TT}(NO3)2(EtOH)] and a rare 3,4‐connected (3,4‐c) topology in [(Cu2I2)3{(4‐py)3TT}4]n ⋅ xn(H2O,EtOH). The multifaceted emissive behaviour of the CPs and the free ligand has been investigated and interpreted through spectroscopic, structural and computational studies. The fluorescence and the high energy phosphorescence of [Ag{(4‐py)3TT}(SO3CF3)]n ⋅ 1/2 ${{ 1/2 }}$ nCH2Cl2, [Cd{(4‐py)3TT}(NO3)2(EtOH)]n and (4 py)3TT itself are correlated to singlet and triplet excited states of molecular origin while their low energy phosphorescence derives from supramolecular entities associated with strong π–π interactions with little metal contribution as it is the case for the single phosphorescence observed for [(Cu2I2)3{(4‐py)3TT}4]n ⋅ xn(H2O,EtOH). In agreement, unusually long lifetimes in the ms regime are measured for crystals of all compounds. [ABSTRACT FROM AUTHOR]

Organic room temperature phosphorescent (ORTP) materials with stimuli-responsive, multicomponent emissive behaviour are extremely desirable for various applications. The derivative of cyclic triimidazole (TT) functionalized with an ethynyl group, TT-CCH, is isolated and investigated. The compound possesses crystallization-enhanced emission (CEE) comprising dual fluorescence and dual phosphorescence of both molecular and supramolecular origin with aggregation-induced components highly sensitive to grinding. The mechanisms involved in the emissions have been disclosed thanks to combined structural, spectroscopic and computational investigations. In particular, strong CH⋯N hydrogen bonds are deemed responsible, for the first time in the TT family, together with frequently observed π⋯π stacking interactions, for the aggregated fluorescence and phosphorescence. [ABSTRACT FROM AUTHOR]

The development of organic room-temperature phosphorescent (ORTP) materials represents an active field of research due to their significant advantages with respect to their organometallic counterparts. Two cyclic triimidazole (TT) derivatives bearing one and three hexyl-thiophene moieties, TT-HThio and TT-(HThio)3, have been prepared and characterized. Both compounds display enhanced quantum yields in their crystalline form with respect to those in a solution state, revealing crystallization-enhanced emissive (CEE) behavior. Importantly, while single fluorescence is observed in solution, crystalline powders also feature dual ORTP, whose respective molecular and aggregate origins have been disclosed through X-ray diffraction analysis and DFT/TDDFT calculations. The relation between the photophysical properties of TT-HThio and its crystallinity degree has been confirmed by a decrease in photoluminescent quantum yield (Φ) and loss of vibronic resolution when its crystals are ground in a mortar, revealing mechanochromic behavior and confirming CEE features. [ABSTRACT FROM AUTHOR]

A QTAIM and IQA investigation on model compounds of two isostructural AgI and CuI coordination polymers (CPs) based on cyclic triimidazole (L), i.e. the [MIL]n 1D double‐stranded stair chain and the [MClL]n 3D network (M = Cu, Ag), has allowed light to be shed on the different emissive behaviour associated with the two metal ions. According to a previously reported investigation [Malpicci et al. (2021). Inorg. Chem. Front.8, 1312–1323], AgI CPs showed both fluorescence and multiple ligand‐centred room‐temperature phosphorescences, whereas CuI CPs displayed non‐thermally equilibrated halogen and metal‐to‐ligand charge transfer and two ligand‐centred phosphorescences, the latter observed only by their selective activation. Analysis of both local and integral QTAIM descriptors, including delocalization indices and source function, of the Ag—N and Cu—N bonds reveals a higher covalent and local character for the latter, explaining the greater metal–ligand electronic communication observed for the Cu compounds. Moreover, IQA investigation shows that the Cu—N bond is characterized by higher interaction energy, due to both higher electrostatic and exchange‐correlation contributions. Analysis on the M—X (M = Ag, Cu; X = I, Cl) bonds, also present in these structures, highlights a much higher covalent and local character with respect to the M—N bonds. [ABSTRACT FROM AUTHOR]