Luminescent Pt(II) Complexes Containing (1-Aza-15-crown-5)dithiocarbamate and (1-Aza-18-crown-6)dithiocarbamate: Mechanochromic and Solvent-Induced Luminescence.

The strong tendency to stack in the solid state and rich luminescence for the Pt(II) complexes makes them potential candidates as new mechanochromic materials and sensing applications. Six mononuclear complexes [Pt(ppy)(ONCS)] (), [Pt(bpy)(ONCS)]ClO (), [Pt(ppy)(ONCS)] (), [Pt(phen)(ONCS)]ClO·CHOH (), [Pt(phen)(ONCS)]ClO (), and [Pt(phen)(ONCS)]ClO (), one dinuclear complex [Pt(phen)(NaONCS)(ClO)]ClO (), and one one-dimensional (1-D) coordination polymer {Pt(bpy)(NaONCS)(ClO)} () were synthesized by reacting [Pt(ppy)Cl], Pt(bpy)Cl, and Pt(phen)Cl (ppy = 2-phenylpyridine, bpy = 2,2'-bipyridine, and phen = 1,10-phenanthroline) with (1-aza-15-crown-5)dithiocarbamate (ONCS) or (1-aza-18-crown-6)dithiocarbamate (ONCS), respectively, which have been isolated and structurally characterized by X-ray diffraction. Neutral complexes and contain no intermolecular Pt(II)···Pt(II) contact, whereas cationic complexes , , , and with ClO as counteranions show alternative intermolecular Pt(II)···Pt(II) contacts of 3.535/4.091, 3.480/5.001, 3.527/4.571, and 3.446/4.987 Å in the solid state, respectively. Interestingly, complex forms a 1-D coordination polymer through coordination between the encapsulated Na ions inside the azacrown ether rings of ONCS and ClO anions with respective intra- and intermolecular Pt(II)···Pt(II) contacts of 3.402 and 3.847 Å in crystal lattices, whereas a dinuclear complex was surprisingly formed and also connected by the encapsulated Na ions and ClO anions with alternative intra- and intermolecular Pt(II)···Pt(II) contacts of 3.650 and 3.677/4.4.372 Å, respectively. Upon excitation, complexes and showed similar vibronic luminescence at 507, 534, and 502, 532 nm, respectively, and the other complexes and - showed broad luminescence with maxima at 537-567 nm. The B3LYP/LanL2DZ calculation was carried out and used to clarify their excited-state properties. In addition, the powder samples for complexes - almost showed no energy shift for the luminescence and significantly those of complexes - exhibited the mechanochromic luminescence upon grinding. It is noted that complexes and only showed minor red shifts (i.e., from 544 to 556 nm for complex and from 551 to 565 nm for complex ), whereas complex exhibited a remarkable red shift from 558 to 603 nm upon grinding. Besides, their luminescence reversibility was also examined toward various solvents.