The ring-opening polymerizations (ROPs) of e-caprolactone (e-CL) and L-lactide (LLA) have been studied using the organocatalysts of diphenyl phosphate (DPP) and 4dimethylaminopyridine (DMAP). The "dual activation" property of DPP and the "bifunctional activation" property of DPP/DMAP were confirmed by the NMR measurement for e-CL and its chain-end model of poly(e-caprolactone) and for LLA and its chain-end model of poly(L-lactide) (PLLA), respectively. The molar ratio of DPP/DMAP was optimized as 1/2 for the ROP of LLA leading to the well-defined PLLA, such as the molecular weight determined from 1 H NMR measurement of 19,200 g mol 21 and the narrow polydispersity of 1.10. Additionally, functional initiators were utilized for producing the end-functionalized PLLAs. The DPP-catalyzed ROPs of e-CL and its analogue cyclic monomers and then the DPP/DMAP-catalyzed ROP of LLA produced block copolymers.

Zn(2+)-induced fluorescence enhancement of the TPEN (N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine)-based ligand, N,N-bis(1-isoquinolylmethyl)-N',N'-bis(pyridylmethyl)ethylenediamine (N,N-1-isoBQBPEN, 1b), has been investigated. Upon Zn(2+) binding, 1b shows a fluorescence increase (ϕZn = 0.028) at 353 and 475 nm. The fluorescence enhancement at longer wavelengths is due to intramolecular excimer formation of two isoquinolines and is specific for Zn(2+); Cd(2+) induces very small fluorescence at 475 nm (ICd/IZn = 10%). The excimer formation of the [Zn(1b)](2+) complex in the excited state is supported by the time-dependent DFT calculation. Neither long-wavelength fluorescence nor excimer formation is observed in the Zn(2+) complex of N,N'-1-isoBQBPEN (2b). The quinoline analog N,N-BQBPEN (1a) exhibits similar but significantly smaller excimer formation. Thermodynamic and kinetic comparisons of Zn(2+) binding properties of ethylenediamine-based hexadentate ligands with pyridines and (iso)quinolines are comprehensively discussed.

Intermolecular interactions regulate the molecular properties in proteins and solutions such as solvatochromic systems. Some of the interactions have to be described at an electronic-structure level. In this study, a commutator for calculating the excitation energy is used for deriving a first-order interacting space (FOIS) to describe the environmental response to solute excitation. The FOIS wave function for a solute-in-solvent cluster is solved by second-order perturbation theory. The contributions to the excitation energy are decomposed into each interaction and for each solvent.

A triple-layer QM/sQM/MM method was developed for accurately describing the excited-state molecular interactions between chromophore and the molecular environment (Hasegawa, J.; Yanai, K.; Ishimura, K. ChemPhysChem 2015, 16, 305). A first-order-interaction space (FOIS) was defined for the interactions between QM and secondary QM (sQM) regions. Moreover, configuration interaction singles (CIS) and its second-order perturbation theory (PT2) calculations were performed within this space. In this study, numerical implementation of this FOISPT2 method significantly reduced the computing time, which realized application to solvatochromic systems, p-coumaric acid in neutral ( p-CA) and anionic forms in aqueous solution, retinal Schiff base in methanol (MeOH) solution, and bacteriorhodopsin (bR). The results were consistent with the experimentally observed absorption spectra of the applied systems. The QM/sQM/MM result for the opsin shift was in better agreement to the experimental result than that of the ordinary QM/MM. A decomposition analysis was performed for the excited-state molecular interactions. Among the electronic interactions, charge-transfer (CT) effect, excitonic interaction, and dispersion interaction showed significant large contributions, while the electronic polarization effect presented only minor contribution. Furthermore, the result was analyzed to determine the contributions from each environmental molecule and was interpreted based on the distance of the molecules from the π system in the chromophores.

Summary:The ring-opening polymerization (ROP) of 1,5-dioxepan-2-one (DXO) catalyzed by diphenyl phosphate (DPP) using 3-phenyl-1-propanol (PPA) as an initiator has been studied. The polymerization in toluene at room temperature produced poly(1,5-dioxepan-2-one) (PDXO) with a narrow polydispersity index. The obtained PDXO possessing a PPA residue at the a-chain end was confirmed by the 1 H NMR and MALDI-TOF MS measurements. The livingness of the ROP of DXO was supported by the kinetic and chain-extension experiments. The diblock and random copolymerizations of DXO and e-caprolactone (CL) afforded respective copolymers. The monomer reactivity ratios were obtained as r DXO ¼ 0.59 and r CL ¼ 1.19 using the Kelen-Tüdös method, and the random copolymers showed different thermal properties corresponding to copolymer compositions.