English

• 1. INTRODUCTION

  Recently, the research of photoluminescent copper(Ⅰ) complexes has attracted extensive attention on account of a variety of advantages such as low cost, environmentally friendly features, tunable phosphorescence emission wave-lengths and so on^[1−12]. Among various copper(Ⅰ) complexes, those containing α-diimine and phosphine as mixed ligands with the first example reported by McMillin's group have become the much concerned forefront complexes^[1−12]. Such noble-metal-free systems have been widely used in photocatalysis^{[11, 12]}, solar energy conversion^[11], OLEDs^[13−15], sometimes smart acid-base response and other fields^[3]. However, one of the drawbacks for such complexes with monophosphines is their instability in solutions^[16]. Therefore, the chelating diphosphine ligands were used instead of monophosphines in order to get better stability^[3−43].

  It is noteworthy that as the typical representatives of α-diimine, phenanthroline and its derivatives were frequently used to assemble luminescent copper(Ⅰ) complexes along with diphosphine owing to their outstanding conjugacy and chelating ability^{[3, 4, 6, 10, 11, 14, 21, 25, 26, 28, 32, 33, 40, 42, 43]}. On the other hand, some examples of Cu(Ⅰ)-diphosphine complexes using 1H-imidazo[4,5-f][1, 10]phenanthrolines (imphens), which are the typical of derivatives of phen, have been reported due to their good phosphorescence at room temperature^{[3, 4, 6, 10, 21]}. Herein, three moderately phosphorescent Cu(Ⅰ) complexes using 2-(2-methoxynaphthyl)-1H-imidazo[4,5-f][1, 10]phenanthroline (mnipH), and the chelating diphosphines bis[(2-diphenylphosphino)phenyl] ether (POP), (±)-2,2'-bis(diphenylphosphino)-1,1'-binaphthalene (BINAP) or 9,9-dimethyl-4,5-bis(diphenylphosphino)-9H-xanthene (xantphos) (Chart 1) as mixed ligands will be reported.

  2. EXPERIMENTAL

  2.1 Materials

  The reagents 5,6-diamino-1,10-phenanthroline (dap), 2-methoxy-1-naphthaldehyde, POP, BINAP, xantphos, the solvents CH₂Cl₂ (DCM) and hexane were purchased from J & K Scientific Ltd, and they are received without further purification. The Cu(Ⅰ) salt [Cu(CH₃CN)₄]ClO₄ was prepared in the light of the published method^[44]. The ligand mnipH and Cu(Ⅰ) complexes were dried through infrared dry technique before use for the photophysical determination.

  2.2 Instruments

  Using Me₄Si as an internal standard and 85% H₃PO₄ as an external standard, respectively, the ¹H and ³¹P NMR spectra in DMSO-d₆ were determined by a Bruker-400 spectrometer. UV-vis absorption spectra were obtained from a Purkinje General TU-1901 UV-vis spectrophotometer. Electrospray ionization mass spectra (ESI-MS) result from the determination from Bruker-micro-TOFQ-MS analyzer with a DCM/methanol mixture as the mobile phase. Steady-state emission spectra result from the determination from Hitachi F4600 fluorescence spectrophotometer.

  Figure Chart 1

  

  Figure Chart 1.  Ligands used in this article

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  2.3 X-ray crystallography

  The single crystals of complexes 2 and 3 from the mother solutions were singled out and quickly enwrapped in vacuum grease and then transferred to a single crystal diffractometer (Bruker Smart APEX Ⅱ) with a stream of cold N₂ followed by data collection at 150 K. The software package CrystalClear 2009, Bruker SAINT was selected for data reduction^{[45, 46]}, and SADABS provided by Bruker was used for absorption correction^[47]. The SHELXL-97 program package was used to solve the two structures by direct methods^[48] and the SHELXL-2014 was used to refine the structures using the full-matrix least-squares method on F² data^[49]. Hydrogen atoms of -NH groups were located by means of difference electron density syntheses and refined freely, and the other hydrogen atoms were generated at theoretically calculated positions followed by the refinement with isotropic U-values on the basis of the corresponding parent atoms. The non-hydrogen atoms were refined anisotropically. The contribution of the DCM solvent molecules in complexes 2 (one DCM molecule) and 3 (three DCM molecules) to the structure factors was removed using the procedure SQUEEZE of program PLATON, while the final refinement was on the basis of the modified structure factors with the usual fashion^[50].

  2.4 Preparation of mnipH and the Cu(Ⅰ) complexes

  2.4.1   2-(2-Methoxynaphthyl)-1H-imidazo[4,5-f][1, 10]phenanthroline (mnipH)

  The mixture of 2-methoxy-1-naphthaldehyde (186.6 mg, 1.00 mmol) and dap (210.4 mg, 1.00 mmol) in ethanol was refluxed at 82 ℃ for 11 h, and then cooled to room temperature. A dark yellow precipitate was obtained after filtration and washed some times by cold ethanol. The crude product was further recrystallized with ethanol and dried under an infrared lamp, and then the final light yellow compound was obtained. Yield: 61.0% (229.5 mg). ¹H NMR (400 MHz, DMSO-d₆, δ, ppm): 13.82 (s, 1H, NH), 9.06 (dd, J = 4.0 Hz, J′ = 1.6 Hz, 2H, Ar-H), 8.92 (dd, J = 8.0 Hz, J′ = 1.2 Hz, 1H, Ar-H), 8.82 (dd, J = 8.0 Hz, J′ = 1.2 Hz, 1H, Ar-H), 8.22 (d, J = 9.2 Hz, 1H, Ar-H), 8.01 (dd, J = 7.6 Hz, J′ = 1.6 Hz, 1H, Ar-H), 7.86–7.81 (m, 2H, Ar-H), 7.74 (d, J = 8.0 Hz, 1H, Ar-H), 7.69 (d, J = 9.2 Hz, 1H, Ar-H), 7.50~7.42 (m, 2H, Ar-H), 3.94 (s, 3H, OCH₃). ESI-MS (m/z): 377.1405 mnipH + H⁺ (calcd. 377.1397) (Fig. S1, Supporting Information).

  2.4.2   [Cu(mnipH)(POP)]ClO₄ (1)

  [Cu(CH₃CN)₄]ClO₄ (16.4 mg, 0.05 mmol) was added to the DCM solution with a mixture of mnipH (18.8 mg, 0.05 mmol) and POP (26.9 mg, 98%, 0.05 mmol), and then the mixture was stirred for 2 h in a dry argon atmosphere at room temperature with the help of Schlenk techniques. After filtration, layering n-hexane warily onto the DCM filtrate gave orange yellow crystals a few days later. The orange-yellow target product was obtained in a 57.6% yield (31.0 mg) after desiccation under an infrared lamp. ¹H NMR (400 MHz, DMSO-d₆, δ, ppm): 14.19 (s, 1H, NH), 9.09 (d, J = 8.0 Hz, 1H, Ar-H), 8.98 (d, J = 8.0 Hz, 1H, Ar-H), 8.87 (d, J = 4.4 Hz, 1H, Ar-H), 8.84 (d, J = 4.8 Hz, 1H, Ar-H), 8.26 (d, J = 9.2 Hz, 1H, Ar-H), 8.04 (dd, J = 7.6 Hz, J′ = 1.2 Hz, 1H, Ar-H), 7.91 (td, J = 8.8 Hz, J′ = 4.8 Hz, 2H, Ar-H), 7.78 (d, J = 8.4 Hz, 1H, Ar-H), 7.73 (d, J = 9.2 Hz, 1H, Ar-H), 7.52~7.44 (m, 4H, Ar-H), 7.34~7.30 (m, 4H, Ar-H), 7.26~7.20 (m, 10H, Ar-H), 7.11 (t, J = 7.6 Hz, 2H, Ar-H), 7.02~6.98 (m, 8H, Ar-H), 6.67~6.63 (m, 2H, Ar-H), 3.97 (s, 3H, OCH₃). ³¹P NMR (400 MHz, DMSO-d₆, δ, ppm): −11.91. ESI-MS (m/z): 977.2159 [Cu(mnipH)(POP)]⁺ (calcd. 977.2230) (Fig. S2, Supporting Information).

  2.4.3   [Cu(mnipH)(xantphos)]ClO₄ (2)

  A similar synthesis and drying procedures as those of 1 was used for complex 2 other than using diphosphine xantphos instead of its analogue POP. Color: golden yellow. Yield: 60.4% (33.7 mg) for 2. ¹H NMR (400 MHz, DMSO-d₆, δ, ppm): 14.18 (s, 1H, NH), 9.07 (d, J = 8.0 Hz, 1H, Ar-H), 8.97 (d, J = 8.0 Hz, 1H, Ar-H), 8.53 (d, J = 4.4 Hz, 2H, Ar-H), 8.27 (d, J = 9.2 Hz, 1H, Ar-H), 8.05 (d, J = 7.6 Hz, 1H, Ar-H), 7.89 (dd, J = 7.8 Hz, J′ = 1.0 Hz, 4H, Ar-H), 7.79 (d, J = 8.4 Hz, 1H, Ar-H), 7.73 (d, J = 9.6 Hz, 1H, Ar-H), 7.55~7.45 (m, 2H, Ar-H), 7.31~7.25 (m, 6H, Ar-H), 7.14 (t, J = 6.8 Hz, 8H, Ar-H), 6.94 (m, 8H, Ar-H), 6.59~6.55 (m, 2H, Ar-H), 3.98 (s, 3H, OCH₃), 1.77 (s, 6H, CH₃). ³¹P NMR (400 MHz, DMSO-d₆, δ, ppm): −12.90. ESI-MS (m/z): 1017.2616 [Cu(mnipH)(xantphos)]⁺ (calcd. 1017.2543), 641.1250 [Cu(xantphos)]⁺ (calcd. 641.1224), 377.1405 mnipH + H⁺ (calcd. 377.1397) (Fig. S3, Supporting Information).

  2.4.4   [Cu(mnipH)(BINAP)]ClO₄ (3)

  A similar synthesis and drying procedures as those of 1 were used for complex 3 other than using diphosphine BINAP instead of its analogue POP. Color: golden yellow. Yield: 85.2% (49.4 mg). ¹H NMR (400 MHz, DMSO-d₆, δ, ppm): 14.30 (s, 1H), 9.27 (d, J = 8.0 Hz, 1H, Ar-H), 9.15 (d, J = 8.0 Hz, 1H, Ar-H), 9.07 (d, J = 4.4 Hz, 1H, Ar-H), 9.03 (d, J = 4.4 Hz, 1H, Ar-H), 8.27 (d, J = 9.2 Hz, 1H, Ar-H), 8.19 (td, J = 8.5 Hz, J′ = 4.8 Hz, 2H, Ar-H), 8.06~8.03 (m, 1H, Ar-H), 7.92 (d, J = 8.8 Hz, 2H, Ar-H), 7.79~7.73 (m, 4H, Ar-H), 7.49~7.44 (m, 4H, Ar-H), 7.38~7.31 (m, 8H, Ar-H), 7.28~7.21 (m, 6H, Ar-H), 7.18~7.13 (m, 4H, Ar-H), 6.87~6.82 (m, 4H, Ar-H), 6.68 (t, J = 7.6 Hz, 4H, Ar-H), 3.97 (s, 3H). ³¹P NMR (400 MHz, DMSO-d₆, δ, ppm): 1.23. ESI-MS (m/z): 1061.2645 [Cu(mnipH)(BINAP)]⁺ (calcd. 1061.2594) (Fig. S4, Supporting Information).

  3. RESULTS AND DISCUSSION

  3.1 Syntheses

  The new ligand mnipH was prepared using a similar procedure reported previously by our group^{[3, 4, 21]}. The mixture of 2-methoxy-1-naphthaldehyde (186.6 mg, 1.00 mmol), dap (210.4 mg, 1.00 mmol) in ethanol was refluxed continuously at 82 ℃ for about 11 h, and then the mixture was cooled naturally to room temperature. After filtration and washing with cold ethanol, a dark yellow precipitate was obtained. Then the recrystallization of the crude product in ethanol was carried out and the light yellow compound was obtained after desiccation under an infrared lamp.

  Complexes 1~3 were synthesized and purified in the light of the procedure reported previously by the reaction of mnipH, diphosphine ligands and [Cu(MeCN)₄]ClO₄ in terms of a 1:1:1 molar ratio followed by the slow crystallization from the hexane/DCM mixed solvents (Scheme 1)^{[3, 4, 6, 10, 21]}.

  Scheme 1

  

  Scheme 1.  Synthetic routes for complexes 1~3

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  3.2 X-ray structure analysis

  Both the refinement details and well-chosen crystallographic data of complexes 2 and 3 are presented in Table S1 (Supporting Information). The well-chosen bond lengths along with bond angles of the corresponding complexes are listed in Table 1. The perspective views of the cations corresponding to complexes 2 and 3 are pictured in Figs. 1 and 2, respectively. An asymmetric unit of complex 3 consists of two [Cu(mnipH)(BINAP)]ClO₄ molecules. Both complexes 2 and 3 reveal mononuclear structures. As in most previously reported Cu(Ⅰ)-1H-imidazo[4,5-f][1, 10]phenanthroline-diphosphine analogues, all the Cu(Ⅰ) centers adopt the distorted tetrahedral geometries accomplished by two nitrogen atoms from the chelating phen coordination sites of mnipH and two phosphorus atoms from diphosphine. The Cu−N distances (2.039(2)~2.087(3) Å) and Cu−P distances (2.206(1)~2.276(1) Å) are much comparable to those in analogues reported previously^{[3, 4, 6, 10, 21]}.

  Table 1

  

  Table 1.  Selected Bond Lengths (Å) and Bond Angles (º) for Complexes 2 and 3

  DownLoad: CSV

  2
  Bond	Dist.		Bond	Dist.		Bond	Dist.
  Cu(1)−N(1)	2.039(2)		Cu(1)−N(2)	2.073(3)		Cu(1)−P(1)	2.206(1)
  Cu(1)−P(2)	2.265(1)		C(13)−N(3)	1.362(4)		C(13)−N(4)	1.319(4)
  Angle	(°)		Angle	(°)		Angle	(°)
  N(1)−Cu(1)−N(2)	81.26(9)		N(1)−Cu(1)−P(1)	122.51(7)		N(1)−Cu(1)−P(2)	106.16(7)
  N(2)−Cu(1)−P(1)	116.03(7)		N(2)−Cu(1)−P(2)	102.58(7)		P(1)−Cu(1)−P(2)	120.36(3)
  3
  Bond	Dist.		Bond	Dist.		Bond	Dist.
  Cu(1)−N(1)	2.087(3)		Cu(1)−N(2)	2.073(3)		Cu(1)−P(1)	2.254(1)
  Cu(2)−N(5)	2.061(3)		Cu(2)−N(6)	2.053(3)		Cu(1)−P(2)	2.276(1)
  Cu(2)−P(3)	2.237(1)		Cu(2)−P(4)	2.242(1)		C(13)−N(3)	1.321(4)
  C(13)−N(4)	1.361(4)		C(81)−N(7)	1.323(4)		C(81)−N(8)	1.365(4)
  Angle	(°)		Angle	(°)		Angle	(°)
  N(1)−Cu(1)−N(2)	80.21(10)		N(1)−Cu(1)−P(1)	111.44(7)		N(1)−Cu(1)−P(2)	121.05(7)
  N(2)−Cu(1)−P(1)	121.45(7)		N(2)−Cu(1)−P(2)	121.62(7)		P(1)−Cu(1)−P(2)	101.28(3)
  N(5)−Cu(2)−N(6)	81.53(10)		N(5)−Cu(2)−P(3)	121.13(8)		N(5)−Cu(2)−P(4)	105.15(8)
  N(6)−Cu(2)−P(3)	122.93(8)		N(6)−Cu(2)−P(4)	120.60(8)		P(3)−Cu(2)−P(4)	103.85(3)

  Figure 1

  

  Figure 1.  Cation structure of complex 2. The phenyl rings of PPh₂ units with most hydrogen atoms omitted for clarity. The thermal ellipsoids were depicted with 30% probability

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  Figure 2

  

  Figure 2.  Cation structure of complex 3. The phenyl rings of the PPh₂ units and most hydrogen atoms are omitted for clarity. The thermal ellipsoids were depicted with 30% probability

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  The bond distances for C(13)−N(3) and C(13)−N(4) in complex 2 are 1.362(4) and 1.319(4) Å, respectively. While in complex 3, the corresponding bond distances for C(13)−N(3) and C(13)−N(4) are 1.321(4) and 1.361(4) Å, and those for C(81)−N(7) and C(81)−N(8) are 1.323(4) and 1.365(4), respectively. The enough large difference values in the range of 0.040~0.043 Å for the above two C−N bond distances within an imidazole ring confirm that the imidazole rings in complexes 2 and 3 have neutral characters^{[3, 4, 6, 10, 21]}.

  The dihedral angles (dhas) between the imidazo[4,5-f][1, 10]phenanthroline plane and the naphthalene ring are 124.77° in complex 2 and 131.94° and 138.91° in complex 3, respectively. These dhas are apparently larger than those 7.7~29.9° in the analogues [Cu(nimpH)(POP)]PF₆, [Cu(nimp)(xantphos)] and [Cu(nimp)(BINAP)] which include the neutral or deprotonation form of 2-(2-naphthyl)-1H-imidazo[4,5-f][1, 10]phenanthroline) (nimpH)^[3]. The larger dhas reveal the relatively larger repulsive force between the imidazo[4,5-f][1, 10]phenanthroline plane and the naphthalene ring owing to the methoxy group in 2-position of naphthyl group.

  As shown in Fig. 3, intramolecular and intermolecular N−H…O hydrogen bonds are observed for complex 3 between imidazole ring and the methoxy group within one mnipH ligand, and between the perchlorate anion and imidazole rings. The N···O distances and N−H···O angles fall in the ranges of 2.680(5)~2.926(5) Å and 109(3)~159(4)° (Table S2), respectively^[6]. Furthermore, intramolecular π···π interactions within the ligand BINAP and intermolecular π···π interactions between mnipH ligands are widely found. It is difficult to show all these weak interactions clearly in a single figure because of the bulky molecules. Therefore, only the latter are discussed here. The quadruple intermolecular aromatic π···π interactions (Table S3 and Fig. 3) are observed between mnipH molecules of two complex 3 cations with the distances between two aromatic rings centroids falling in the range of 3.452~3.674 Å^[6]. The quadruple intermolecular π…π interactions and hydrogen bonds between perchlorate anion and imidazole rings lead to the formation of the dimer of complex 3.

  Figure 3

  

  Figure 3.  Cation dimer resulting from the intermolecular π…π interactions of complex 3 along with the intramolecular and intermolecular hydrogen bonds. The phenyl rings of PPh₂ units, one perchlorate anion and most hydrogen atoms are omitted for clarity. Symmetry code for B: x − 1, y, z − 1

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  3.3 ¹H and ³¹P NMR spectra

  The ¹H NMR spectra corresponding to the free mnipH ligand and copper(Ⅰ) complexes 1~3 in DMSO-d₆ are pictured in Figs. S5~S8 (Supporting Information). While the ³¹P NMR spectra corresponding to all the copper(Ⅰ) complexes are depicted in Fig. S9. The ¹H NMR spectra are in good accordance with the homologous structures, and the signals in the range of 13.82~14.30 ppm corresponding to the -NH group arising from mnip ligands in free or in coordination states are comparable to the corresponding values reported previously^{[3, 4, 6, 10, 21]}. Only single ³¹P NMR signal for each copper(Ⅰ) complex was observed, signifying that the two phosphorus atoms within each copper(Ⅰ) complex are really equivalent in solution^{[3, 4, 6, 10]}.

  3.4 Physical properties

  3.4.1   Absorption spectra

  UV-vis electronic absorption spectra and data in DCM with the concentration at 2.5 × 10⁻⁵ mol·L⁻¹ of mnipH and all the copper(Ⅰ) complexes at 298 K are depicted in Fig. 4 and Table 2, respectively. The absorptions of mnipH with the wavelength less than 400 nm are principally attributed to π → π* transition character of the ligands, probably mixed with a few n → π* transition characters of mnipH. Compared to those absorptions of mnipH and the previously reported Cu(Ⅰ)-imphens-PP systems^{[3, 4, 6, 10, 24]}, the intense absorption bands prior to 395 nm for the copper(Ⅰ) complexes are tentatively and principally attributed to π → π* transitions of mnipH and the diphosphine ligands together with certain spin-forbidden n → π* transition character of mnipH^{[3, 4, 6, 10, 24]}. While the newly emerging, relatively weak wide absorptions at relatively lower energy bands of the copper(Ⅰ) complexes with the maximum absorption wavelengths within the range of 417~421 nm are principally attributed to metal-to-ligand charge transfer (MLCT), dπ(Cu) → π*(mnipH) transitions^{[3, 4, 6, 10]}.

  Figure 4

  

  Figure 4.  UV-Vis absorption spectra of mnipH and all complexes in DCM at room temperature

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  Table 2

  

  Table 2.  Photophysical Data of All Complexes at Room Temperature

  DownLoad: CSV

  Compound	λabs/nm (ε/M-1cm-1) (DCM)	λem/nm (solid)
  mnipH	291 (25440), 352 (16000)
  1	296 (34800), 353 (18400), 417 (6080)	601
  2	292 (38600), 354 (19160), 417 (6200)	602
  3	294 (39600), 346 (21240), 421 (8240)	604

  3.4.2   Photoluminescence (PL)

  All the copper(Ⅰ) complexes give moderate photoluminescence in the solid state, as illustrated in Fig. 5 and Table 2. The emission with the maxima in the range of 601~604 nm is principally attributable to ³MLCT phosphorescence in accordance with those previously reported in the Cu(Ⅰ)-Imphens-PP analogs^{[3, 4, 6, 10]}. By contrast, all the copper(Ⅰ) complexes show extremely weak, even negligible photoluminescence in DCM solutions at 298 K, which might be on account of the high energy vibration caused by N−H bonds, other possible intramolecular vibration and rotation as well as the luminescent quenching caused by oxygen in air^{[3, 4, 6, 10]}. While the relatively more intense luminescence of copper(Ⅰ) complexes in the solid state compared with that in solutions is principally attributed to the restriction of intramolecular vibration and rotation caused by the aggregation-induced behaviour.

  Figure 5

  

  Figure 5.  Photoluminescence spectra of all complexes in the solid state (left) with an excitation wavelength at 365 nm and luminescence images under 365 nm excitation with a hand-held ultraviolet light (right)

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  4. CONCLUSION

  Three ionic copper(Ⅰ) complexes with 2-(2-methoxyna-phthyl)-1H-imidazo[4,5-f][1, 10]phenanthroline and the chelating diphosphine as mixed ligands have been successfully synthesized and well characterized. All the copper(Ⅰ) complexes emit moderate phosphorescence in the solid state.

  
  
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  Figure Chart 1  Ligands used in this article

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  Scheme 1  Synthetic routes for complexes 1~3

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  Figure 1  Cation structure of complex 2. The phenyl rings of PPh₂ units with most hydrogen atoms omitted for clarity. The thermal ellipsoids were depicted with 30% probability

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  Figure 2  Cation structure of complex 3. The phenyl rings of the PPh₂ units and most hydrogen atoms are omitted for clarity. The thermal ellipsoids were depicted with 30% probability

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  Figure 3  Cation dimer resulting from the intermolecular π…π interactions of complex 3 along with the intramolecular and intermolecular hydrogen bonds. The phenyl rings of PPh₂ units, one perchlorate anion and most hydrogen atoms are omitted for clarity. Symmetry code for B: x − 1, y, z − 1

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  Figure 4  UV-Vis absorption spectra of mnipH and all complexes in DCM at room temperature

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  Figure 5  Photoluminescence spectra of all complexes in the solid state (left) with an excitation wavelength at 365 nm and luminescence images under 365 nm excitation with a hand-held ultraviolet light (right)

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  Table 1.  Selected Bond Lengths (Å) and Bond Angles (º) for Complexes 2 and 3

  2
  Bond	Dist.		Bond	Dist.		Bond	Dist.
  Cu(1)−N(1)	2.039(2)		Cu(1)−N(2)	2.073(3)		Cu(1)−P(1)	2.206(1)
  Cu(1)−P(2)	2.265(1)		C(13)−N(3)	1.362(4)		C(13)−N(4)	1.319(4)
  Angle	(°)		Angle	(°)		Angle	(°)
  N(1)−Cu(1)−N(2)	81.26(9)		N(1)−Cu(1)−P(1)	122.51(7)		N(1)−Cu(1)−P(2)	106.16(7)
  N(2)−Cu(1)−P(1)	116.03(7)		N(2)−Cu(1)−P(2)	102.58(7)		P(1)−Cu(1)−P(2)	120.36(3)
  3
  Bond	Dist.		Bond	Dist.		Bond	Dist.
  Cu(1)−N(1)	2.087(3)		Cu(1)−N(2)	2.073(3)		Cu(1)−P(1)	2.254(1)
  Cu(2)−N(5)	2.061(3)		Cu(2)−N(6)	2.053(3)		Cu(1)−P(2)	2.276(1)
  Cu(2)−P(3)	2.237(1)		Cu(2)−P(4)	2.242(1)		C(13)−N(3)	1.321(4)
  C(13)−N(4)	1.361(4)		C(81)−N(7)	1.323(4)		C(81)−N(8)	1.365(4)
  Angle	(°)		Angle	(°)		Angle	(°)
  N(1)−Cu(1)−N(2)	80.21(10)		N(1)−Cu(1)−P(1)	111.44(7)		N(1)−Cu(1)−P(2)	121.05(7)
  N(2)−Cu(1)−P(1)	121.45(7)		N(2)−Cu(1)−P(2)	121.62(7)		P(1)−Cu(1)−P(2)	101.28(3)
  N(5)−Cu(2)−N(6)	81.53(10)		N(5)−Cu(2)−P(3)	121.13(8)		N(5)−Cu(2)−P(4)	105.15(8)
  N(6)−Cu(2)−P(3)	122.93(8)		N(6)−Cu(2)−P(4)	120.60(8)		P(3)−Cu(2)−P(4)	103.85(3)

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  Table 2.  Photophysical Data of All Complexes at Room Temperature

  Compound	λabs/nm (ε/M-1cm-1) (DCM)	λem/nm (solid)
  mnipH	291 (25440), 352 (16000)
  1	296 (34800), 353 (18400), 417 (6080)	601
  2	292 (38600), 354 (19160), 417 (6200)	602
  3	294 (39600), 346 (21240), 421 (8240)	604

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