FULL PAPER DOI:10.1002/ejic.201402712 Controlled Linker Dependence of Solution- and Solid- State Emission of Vaulted trans-Bis(salicylaldiminato)- platinum(II) Complexes with Amino Functionalities Naruyoshi Komiya, [a] Minoru Okada, [a] Makoto Hoshino, [a] Ngoc Ha-Thu Le, [a] and Takeshi Naota* [a] Keywords: Platinum / Salicylaldiminato complexes / Solid-state structures / Solid-state emission / Acid-induced emission enhancement / Luminescence The synthesis, structures, and emission properties of vaulted trans-bis(salicylaldiminato)platinum(II) complexes 1 with di- ethylamino functionalities are described and compared with the non-substituted analogues. The amino substitution pro- vides an improvement of the linker dependence both for the color change of the trans-bis(salicylaldiminato)platinum(II) platform in the glass state and for the acid-induced emission enhancement in the solution state. The linker dependence of the crystalline-state emission intensity changes with the Introduction Transition-metal complexes bearing vaulted structures have attracted much interest as potential functional materi- als because of their picnic-basket-shaped 3D structures, which include bridged ligands and square-planar coordina- tion planes. [1–3] A variety of vaulted complexes have been prepared by the reaction of square-planar transition-metal centers with tether-linked ligands, which include por- phyrin, [4] 2,2-diiminoenamine, [5] o-iminophenol, [6] β-imino- ketones, [7] o-iminopyrrole, [8] o-carbamoylpyridine, [8b] 2,2'- bis(phosphanyl)-1,1'-biferrocene, [9] 1,3-bis(2-pyridylethyn- yl)benzene, [10] 2-aminophenol, [11] 2-aminotropone, [12] and N-heterocyclic carbene. [13] The correlation between the structures and functions has been extensively studied in view of their inclusion properties, [4d,5,6d] molecular aggrega- tion, [6b,6c,12] optical properties, [4e,6c,6e,6f,13b] and catalytic ac- tivity for organic transformations. [4a–4c,9,13a] As part of our program aimed at the development of new organometallic phosphorescent materials, we have found that various polymethylene- and polyoxyethylene-vaulted platinum(II) analogues bearing 3D superstructures exhibit intense phosphorescence in the crystalline state, [6e,6f] where [a] Department of Chemistry, Graduate School of Engineering Science, Osaka University Machikaneyama, Toyonaka, Osaka 560-8531, Japan E-mail: naota@chem.es.osaka-u.ac.jp http://www.soc.chem.es.osaka-u.ac.jp/english/index.html Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/ejic.201402712. Eur. J. Inorg. Chem. 2014, 6085–6096 © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 6085 amino functionality, which leads to intense emission of the vaulted crystals with low structural dependence. Single-crys- tal X-ray diffraction studies and DFT calculations revealed that the unique photophysical properties arising from the amino functionality are attributable to enhanced planarity and self-constraint of the coordination platform, which is due to their strong contribution to d–π conjugation and inter- molecular hydrogen bonding. the specific heat resistance towards emission decay with in- creasing temperature was determined to be essential for in- tense phosphorescence at ambient temperature. Single-crys- tal X-ray diffraction (XRD) studies strongly suggest that the linker-dependent control of the coordination planarity of the trans-bis(salicylaldiminato)platinum platform and the subsequent higher-order molecular constraint by inter- molecular interactions are key factors for the crystals to exhibit intense solid-state emission and heat-resistance properties. To gain further insight into the intra- and intermolecular factors governing the emission properties of these vaulted Pt II complexes, the effect of the amino functionality in poly- methylene-vaulted trans-bis(salicylaldiminato)-platinum(II) complexes was investigated, and the main aim was to re- motely control the d–π conjugation of the emissive plat- form. We found that the introduction of 4-diethylamino groups into the aromatic rings of vaulted Pt II complexes results in unique linker-dependent controllability of the color change and the acid-induced emission enhancement in the glass and solution states of these compounds. The amino functionalities also decrease the linker dependence of the heat resistance in the crystalline state, which leads to intense solid-state emission of the vaulted crystals with low structural dependence. XRD studies and DFT calculations indicate that the amino functionalities enhance d–π conju- gation within the coordination platforms and inter- molecular hydrogen interactions, which provides the ration- ale for these unique photophysical properties. Here, we de-