Elsevier

Journal of Molecular Structure

Volume 1191, 5 September 2019, Pages 95-100
Journal of Molecular Structure

Two Cu(I) complexes constructed by different N-heterocyclic benzoxazole ligands: Syntheses, structures and fluorescent properties

https://doi.org/10.1016/j.molstruc.2019.04.108Get rights and content

Highlights

  • A tri-coordinated Cu(I) coordination polymer 1 with planar trigonal configuration.

  • A four-coordinated mononuclear Cu(I) complex 2 possessing a slightly distorted trigonal pyramidal geometry.

  • There are excellent fluorescence properties of the complexes 1 and 2 in a solid state.

Abstract

Reaction of 2,2-(1,4-butanediyl)bis-1,3-benzoxazole (BBO) or 2-(2′-pyridyl)benzoxazole (PBO) ligands with [Cu(CH3CN)2(PPh3)2](BF4) afforded a copper(I) coordination polymer {[Cu(BBO)(PPh3)](BF4)}n (1) and a mononuclear copper(I) complex [Cu(PBO)(PPh3)2](BF4)·2CH2Cl2 (2) (where PPh3 = triphenylphosphine), which have been characterized by elemental analysis, IR spectra and single-crystal X-ray diffraction. The structural analysis revealed that in complex 1, copper(I) ions are three-coordinated and the geometric structure around the central copper(I) atom can be described as planar trigonal configuration. Complex 1 exhibits an one-dimensional coordination polymer by two BBO bridging adjacent copper(I) ions, forming a single-stranded meso-helical chain structure. Mononuclear complex 2 is four-coordinated and slightly distorted triangular-pyramid geometry. Solid luminescence properties investigation show that complex 1 has two emission peaks, which attributed to the π*-π and π*-n transitions. However complex 2 only has one emission peak, which may be attributed to MLCT [d10(Cu)→π*]. This indicates that different types of N-heterocyclic ligands have an important influence on the structure and luminescent properties of copper(I) complexes.

Graphical abstract

Two Cu(I) complexes with different N-heterocyclic benzoxazole ligands were synthesized. The tri-coordinated copper(I) coordination polymer 1 can be described as planar trigonal configuration. The four-coordinated mononuclear copper(I) complex 2 possess a slightly distorted trigonal pyramidal geometry. The photoluminescent transition of Cu(I) complex 2 may be attributed to metal-to-ligand charge-transfer [MLCT].

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Introduction

The cuprous chemistry have drawn special attention because of their unusual structural features and various applications ranging from biological sensors and interesting physical properties to catalysis, optics and luminescent materials [1]. They are being environmentally friendly, less expensive, intriguing coordination modes and exhibit rich photochemical and photophysical properties [2], especially in the promising application as emissive thermally-activated delayed fluorescence (TADF) materials in OLEDs [3]. The combination of the electron rich copper(I) center, conjugated organic ligand and high degree of inherent covalence in soft acid-soft base bonding can produce low energy electronic interactions between metal center and the ligand, and the resulting compounds possess interesting optical and electronic properties [4].

Benzoxazoles and their derivatives are part of an important class of N-heterocycles which can not only have shown strong coordination ability to the transition metal ions, but also exhibit remarkable features such as ease of preparation, electrochemical behavior, light absorption in the visible region, characteristic structural flexibility, supramolecular architecture, long-lived electronically excited states, intense luminescent and biological activity [5]. A lot of N-heterocyclic copper(I) complexes such as discrete monomers, multinuclear clusters and coordination polymers have been reported by several research groups [6]. In these complexes, the N-heterocyclic ligands play an important role in determining the overall structure of the copper(I) complexes and consequently their photophysical properties [6,7]. Therefore, the appropriate selection of N-heterocyclic ligands appeared as one key point to tune and improve the structures and properties of copper(I) species, which can be highly affected via the steric, electronic, and conformational effects [8]. Herein, two N-heterocyclic benzoxazole ligands combined with the [Cu(CH3CN)2(PPh3)2](BF4) were employed to obtain two copper(I) complexes. The structures of the two complexes have been characterized by elemental analysis, IR spectra and X-ray single crystal diffraction. In addition, their fluorescent properties have been studied.

Section snippets

Materials and general methods

The ligands BBO and PBO were prepared according to the literature procedure [9]. [Cu(CH3CN)2(PPh3)2](BF4) was synthesized on the basis of literature procedures [10]. All reactions were carried out under a nitrogen atmosphere, using anhydrous solvents or solvents treated with an appropriate drying reagent. Commercially available reagents were used without further purification unless otherwise stated. The C, H and N elemental analyses were determined using a Carlo Erba 1106 elemental analyzer.

Results and discussion

Two new copper(I) complexes were synthesized by solvent diffusion method. The synthetic routes to copper(I) complexes are shown in Scheme 1. The elemental analyses of two complexes are in good agreement with the theoretical compositions. The copper(I) complexes are remarkably soluble in polar aprotic solvents such as DMF, DMSO, dichloromethane and acetonitrile, slightly soluble in ethanol and methanol, and insoluble in water, diethyl ether, petroleum ether and hexane.

Conclusion

In this paper, two copper(I) complexes with N-heterocyclic ligands were synthesized and characterized. The structural analysis revealed that complex 1 is three-coordinated trigonal planar geometry, while mononuclear complex 2 is a four-coordinated slightly distorted triangular-pyramidal environment. In complex 1, the BBO ligand adopts the μ2-bridging mode to link two copper(I) atoms forming an one-dimensional single-stranded meso-helix chain coordination polymer. In addition, complexes 1 and 2

Supplementary data

Crystallographic data (excluding structure factors) for the structures reported in this paper have been deposited with the Cambridge Crystallographic Data Center with reference numbers CCDC 1549239 and 1848400. Copies of the data can be obtained, free of charge, on application to the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK. Tel.:+44 01223 762 910; fax: +44 01223 336 033; e-mail: [email protected] or http://www.ccdc.cam.ac.uk.

Acknowledgments

The present research was supported Foundation of A Hundred Youth Talents Training Program of Lanzhou Jiaotong University (Grant No. 152022), Natural Science Foundation of Gansu Province (Grant No. 17JR5RA090) and National Natural Science Foundation of China (Grant No. 21367017).

References (24)

  • K. Fujisawa et al.

    Inorg. Chem.

    (2007)
  • C. Janiak

    J. Chem. Soc. Dalton Trans.

    (2000)
    H.L. Wu et al.

    J. Coord. Chem.

    (2015)
    H.L. Wu et al.

    Appl. Organomet. Chem.

    (2015)
    H.L. Wu et al.

    New J. Chem.

    (2014)
  • J.L. Chen et al.

    Inorg. Chem.

    (2013)
  • H.L. Wu et al.

    Dalton Trans.

    (2012)
    H.L. Wu et al.

    Res. Chem. Intermed.

    (2015)
    H.L. Wu et al.

    J. Photochem. Photobiol., B

    (2012)
    H.L. Wu et al.

    Inorg. Chim. Acta

    (2012)
    J.H. Hu et al.

    New J. Chem.

    (2015)
    H. Zhang et al.

    J. Coord. Chem.

    (2016)
  • H.V.R. Dias et al.

    J. Am. Chem. Soc.

    (2005)
    D.R. McMillin et al.

    Chem. Rev.

    (1998)
    N. Armaroli et al.

    Top. Curr. Chem.

    (2007)
    T. Bessho et al.

    Chem. Comm.

    (2008)
    S. Perruchas et al.

    J. Am. Chem. Soc.

    (2010)
    X. Huang et al.

    Angew. Chem. Int. Ed.

    (2018)
  • N. Armaroli et al.

    Photochemistry and photophysics of coordination compounds: copper

  • G. Baryshnikov et al.

    Chem. Rev.

    (2017)
    G. Grybauskaite-Kaminskiene et al.

    J. Mater. Chem. C

    (2018)
  • L.X. Hu et al.

    Inorg. Chem.

    (2017)
    S. Suckert et al.

    Inorg. Chem.

    (2017)
    S.K. Gibbons et al.

    Inorg. Chem.

    (2017)
    S.Z. Zhan et al.

    Inorg. Chem.

    (2017)
    Y.L. Xu et al.

    Appl. Organomet. Chem.

    (2018)
    Y.L. Xu et al.

    Inorg. Chim. Acta

    (2018)
  • D. Marcinkowski et al.

    Polyhedron

    (2018)
    S. Chacko et al.

    J. Med. Chem.

    (2018)
    J. Huang et al.

    Bioorg. Med. Chem.

    (2018)
    C.S. Abeywickrama et al.

    Tetrahedron Lett.

    (2017)
    A. Belal et al.

    Res. Chem. Intermed.

    (2017)
    S. Pappuru et al.

    Dalton Trans.

    (2017)
    L. Kuhlmann et al.

    Dalton Trans.

    (2018)
  • F. Wei et al.

    CrystEngComm

    (2014)
    N. Armaroli et al.

    Adv. Mater.

    (2006)
    Q. Zhang et al.

    Adv. Mater.

    (2004)
    M. Nishikawa et al.

    J. Am. Chem. Soc.

    (2010)
  • T. McCormick et al.

    Inorg. Chem.

    (2006)
    D.G. Cuttell et al.

    J. Am. Chem. Soc.

    (2002)
    C.S. Smith et al.

    J. Am. Chem. Soc.

    (2010)
  • A. Tsuboyama et al.

    Inorg. Chem.

    (2007)
    P.C. Ford et al.

    J. Bourassa. Chem. Rev.

    (1999)
    S.S. Mao et al.

    Spectrochim. Acta

    (2018)
    H. Zhang et al.

    RSC Adv.

    (2016)
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