Predominance of bridging coordination in luminescent 1,1′- biisoquinoline silver(I) derivatives

Article abstract of DOI:10.1016/j.ica.2012.01.059

A series of di- and polynuclear silver(I) complexes of stoichiometry [Ag(biisoq)₂]_nX_n and [AgX(biisoq)] (biisoq = 1,1′-biisoquinoline, X = CF₃SO₃, BF₄), or [(μ-biisoq)_n(AgXL)₂] (n = 1, 2; L = PPh₃, PMePh₂; X = CF₃SO₃, ClO₄) have been prepared. During crystallization experiments to obtain single crystals the compounds can coordinate solvent or water giving the corresponding derivatives. Seven X-ray diffraction structures have been solved. Different roles of the biisoquinoline ligand are found, but all the structures have in common that it always acts as bridging ligand. Compound [(μ-biisoq){Ag(OSO ₂CF₃)(PPh₃)}{Ag(OH₂)(PPh ₃)}](CF₃SO₃) (3a) shows a single biisoquinoline bridge and tricoordinated silver centres, whilst derivatives [(μ-biisoq)₂{Ag(acetone)(PPh₃)}₂](ClO ₄)₂ (8a), [(μ-biisoq)₂{Ag(OClO ₃)(PMePh₂)}₂] (9), and [(μ-biisoq) ₂{Ag(OSO₂CF₃)(PMePh₂)}₂] (10) display double biisoquinoline bridging ligands and tetracoordinated silver centres, with intramolecular silver-silver distances in the range 3.684-4.434 . Compounds [(μ-biisoq)₂{Ag(OSO₂CF₃)(acetone)} ₂]·2acetone (6a), [(μ-biisoq)₂{Ag(OSO ₂CF₃)(acetone)}₂] (6b), and [(μ-biisoq)Ag(OH₂)₂(μ-biisoq)Ag]_n(CF ₃SO₃)_2n (6c), correspond either to a biisoquinoline-double bridged dimer with short intramolecular argentophilic silver-silver distances of 3.0737(6) (6a) or 3.1358(6) (6b), or to an infinite biisoquinoline-single bridged 1D polymer (6c). In these complexes, the silver centres are either linear 2-coordinate or distorted tetrahedral 4-coordinate. The silver coordination sphere is completed by the anion and in some cases by solvent (acetone, water). Complexes [Ag(biisoq)₂]_nX _n (X = SO₃CF₃ (1); BF₄ (2)) are oligomeric with bridging biisoquinoline, at least in solution. All the derivatives are luminescent at room temperature in the solid state with emission maxima in the range 397-519 nm; they emit at 77 K from 366 to 523 nm. They also emit in CH₂Cl₂ at 298 K in the range 376-490 nm, whilst they are luminescent at 77 K in the range 376-402 nm.

Full text of DOI:10.1016/j.ica.2012.01.059

Inorganica Chimica Acta 386 (2012) 93–101
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Predominance of bridging coordination in luminescent 1,10-biisoquinoline
silver(I) derivatives
⇑
⇑
Manuel Bardají , Ana B. Miguel-Coello, Pablo Espinet
IU CINQUIMA/Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, E-47071 Valladolid, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of di- and polynuclear silver(I) complexes of stoichiometry [Ag(biisoq)2]nXn and [AgX(biisoq)]
(biisoq = 1,10-biisoquinoline, X = CF3SO3, BF4), or [(
l-biisoq)n(AgXL)2] (n = 1, 2; L = PPh3, PMePh2;
Received 8 December 2011
Received in revised form 12 January 2012
Accepted 27 January 2012
Available online 7 February 2012
X = CF3SO3, ClO4) have been prepared. During crystallization experiments to obtain single crystals the
compounds can coordinate solvent or water giving the corresponding derivatives. Seven X-ray diffraction
structures have been solved. Different roles of the biisoquinoline ligand are found, but all the structures
have in common that it always acts as bridging ligand. Compound [(
(OH2)(PPh3)}](CF3SO3) (3a) shows a single biisoquinoline bridge and tricoordinated silver centres, whilst
derivatives [( -biisoq)2{Ag(acetone)(PPh3)}2](ClO4)2 (8a), [( -biisoq)2{Ag(OClO3)(PMePh2)}2] (9), and
[( -biisoq)2{Ag(OSO2CF3)(PMePh2)}2] (10) display double biisoquinoline bridging ligands and tetracoordi-
nated silver centres, with intramolecular silver–silver distances in the range 3.684–4.434 Å. Compounds
[( -biisoq)2{Ag(OSO2CF3)(acetone)}2] (6b), and [(
-biisoq)2{Ag(OSO2CF3)(acetone)}2]ꢀ2acetone (6a), [(
biisoq)Ag(OH2)2( -biisoq)Ag]n(CF3SO3)2n (6c), correspond either to a biisoquinoline-double bridged dimer
l-biisoq){Ag(OSO2CF3)(PPh3)}{Ag
Keywords:
Biisoquinoline
Silver
Luminescence
X-ray crystal structures
Bridging ligand
Atropisomer
l
l
l
l
l
l-
l
with short intramolecular argentophilic silver–silver distances of 3.0737(6) Å (6a) or 3.1358(6) Å (6b), or to
an infinite biisoquinoline-single bridged 1D polymer (6c). In these complexes, the silver centres are either
linear 2-coordinate or distorted tetrahedral 4-coordinate. The silver coordination sphere is completed by
the anion and in some cases by solvent (acetone, water). Complexes [Ag(biisoq)2]nXn (X = SO3CF3 (1); BF4
(2)) are oligomeric with bridging biisoquinoline, at least in solution. All the derivatives are luminescent
at room temperature in the solid state with emission maxima in the range 397–519 nm; they emit at
77 K from 366 to 523 nm. They also emit in CH2Cl2 at 298 K in the range 376–490 nm, whilst they are lumi-
nescent at 77 K in the range 376–402 nm.
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
Ligands incorporating a 1,l0-binaphthyl unit display helical
structures, which gives rise to rotational isomers (atropisomers)
Polydentate nitrogen heterocycles play an important role in
coordination chemistry and crystal engineering, because of their
good coordinating properties and their ability to transmit elec-
tronic effects [1]. Systems containing silver(I) centres are specially
interesting due to the high affinity of silver to N donor ligands, its
flexible coordination number and geometry [2], and the possibility
of forming AgꢀꢀꢀAg weak interaction in some cases [3]. Moreover,
apparently small changes, for instance in the counter-anion or
the solvent, can lead to significant changes in the structures ob-
associated to the high rotational barrier about the C1–C10
r-bond
[6]. This is the case of 1,10-biisoquinoline, for which a DFT theoret-
ical study concluded that the most stable structure is the anti-iso-
mer (good to act as bridge) and displays a N–C–C0–N0 torsional
angle of 129.9°. Its atropisomer, the syn isomer (good to act as che-
late), displays a torsional angle of 26.5°, and the calculated atrop-
isomeric transition barrier is 123.09 kJ/mol [7]. In spite of this
calculated barrier 1,10-biisoquinoline behaves as a flexible ligand
that can modify the torsion angle between the two isoquinoline
halves allowing for monodentate, bidentate bridging and, most of-
ten, bidentate chelating modes of coordination [8]. This behavior is
controlled mainly by the number of auxiliary ligands in the metal-
lic fragment and by their steric requirements. Here we report the
synthesis and characterization of mono-, di- and poly-nuclear
1,10-biisoquinoline silver(I) compounds, where the versatility of
coordination of Ag(I) allows for a variety of coordination modes
of the biisoquinoline ligand. Most of the complexes are lumines-
cent, both in solution and in the solid state.
tained [4]. Although there are many reports on luminescent d10
metal complexes, emissive Ag(I) complexes have been less studied
because of their potential photosensitivity and limited lumines-
cence [5].
-
⇑
Corresponding authors.
E-mail address: espinet@qi.uva.es (P. Espinet).
0020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2012.01.059

94
M. Bardají et al. / Inorganica Chimica Acta 386 (2012) 93–101
X = ClO4, R = Me, R0 = Ph 82 mg) was added biisoquinoline
2. Experimental
(0.1 mmol, 26 mg). The mixture was stirred for 1 h protected from
the light. The solution was concentrated to ca. 5 mL. The addition
of diethyl ether afforded compounds 3–5 as white solids. Yield of
3: 92 mg, 71%. Anal. Calc. for C, 51.95; H, 3.27; N, 2.16. Found: C,
51.65; H, 3.1; N, 2.38%. 1H NMR (CDCl3): d 7.03–7.42 (m, 30H,
Ph), 7.50 (d, JHH = 8.2 Hz, 2H, H8), 7.63 (t, JHH = 7.6 Hz, 2H, H7),
7.73 (d, JHH = 5.7 Hz, 2H, H4), 7.82 (t, JHH = 7.7 Hz, 2H, H6), 7.87 (d,
JHH = 8.2 Hz, 2H, H5), 8.59 (d, JHH = 5.7 Hz, 2H, H3). 1H NMR
(ꢁ55 °C, CDCl3): d 6.75–7.45 (m, 34H, Ph + H8 + H7), 7.69 (t,
JHH = 7.6 Hz, 2H, H6), 7.81 (d, JHH = 7.7 Hz, 2H, H5), 7.85 (d,
JHH = 5.7 Hz, 2H, H4), 8.61 (d, JHH = 5.7 Hz, 2H, H3). 19F NMR (CDCl3):
For general procedures see Supplementary data. Literature
methods were used to prepare 1,10-biisoquinoline [8k] [Ag(CF3SO3)
(PRR02)] [9] and [Ag(OClO3)(PRR02)] [10].
2.1. Synthesis of [Ag(biisoq)2]nXn, X = CF3SO3 (1), X = BF4 (2) and
[AgX(biisoq)], X = CF3SO3 (6), X = BF4 (7)
To a diethyl ether solution (20 mL) of AgX (0.2 mmol; X = CF3SO3
51 mg, X = BF4 39 mg) was added the corresponding biisoquinoline
in the adequate molar ratio 1:2 (102 mg, 0.4 mmol) or 1:1 (51 mg,
0.2 mmol), and the reaction stirred for 60 min protected from the
light. The insoluble compounds were filtered off, washed and dried.
Compounds 1–2 and 6–7 were obtained as white solids. Yield of 1:
135 mg, 88%. Anal. Calc. for C, 57.75; H, 3.14; N, 7.28. Found: C,
57.44; H, 3.41; N, 7.16%. 1H NMR (CDCl3): d 7.46 (d, JHH = 8.3 Hz,
1H, H8), 7.50 (t, JHH = 8.3 Hz, 1H, H7), 7.70 (d, JHH = 5.7 Hz, 1H, H4),
7.77 (t, JHH = 8.3 Hz, 1H, H6), 7.93 (d, JHH = 8.3 Hz, 1H, H5), 8.40 (d,
JHH = 5.7 Hz, 1H, H3). 19F NMR (CDCl3): d ꢁ78.3 (s). 1H NMR (d6-ace-
tone): d 7.49 (d, JHH = 8.3 Hz, 1H, H8), 7.54 (t, JHH = 7.7 Hz, 1H, H7),
7.88 (t, JHH = 7.5 Hz, 1H, H6), 8.04 (d, JHH = 5.7 Hz, 1H, H4), 8.14 (d,
JHH = 7.9 Hz, 1H, H5), 8.45 (d, JHH = 5.7 Hz, 1H, H3). 1H NMR
(ꢁ55 °C, d6-acetone): d 7.31 (d, JHH = 8.5 Hz, 1H, H8), 7.52 (t,
JHH = 7.7 Hz, 1H, H7), 7.93 (t, JHH = 7.1 Hz, 1H, H6), 8.03–8.06 (br,
2H, H3 + H4), 8.23 (d, JHH = 8.3 Hz, 1H, H5). IR (KBr): 1254, 637
(CF3SO3) cmꢁ1. Yield of 2: 106 mg, 75%. Anal. Calc. for C, 61.13; H,
3.42; N, 7.92. Found: C, 61.17; H, 3.71; N, 7.57%. 1H NMR (CDCl3): d
7.35 (d, JHH = 8.4 Hz, 1H, H8), 7.40 (t, JHH = 8.3 Hz, 1H, H7), 7.73 (t,
JHH = 7.3 Hz, 1H, H6), 7.91 (d, JHH = 5.7 Hz, 1H, H4), 8.01 (d,
JHH = 8.3 Hz, 1H, H5), 8.14 (d, JHH = 5.7 Hz, 1H, H3). 19F NMR (CDCl3):
d ꢁ152.9 (s). 1H NMR (d6-acetone): d 7.41 (d, JHH = 8.3 Hz, 1H, H8),
7.55 (t, JHH = 7.3 Hz, 1H, H7), 7.87 (t, JHH = 7.8 Hz, 1H, H6), 8.01 (d,
JHH = 5.7 Hz, 1H, H4), 8.14 (d, JHH = 8.3 Hz, 1H, H5), 8.31 (d,
JHH = 5.7 Hz, 1H, H3). 1H NMR (ꢁ55 °C, d6-acetone): d 7.30 (d,
JHH = 8.6 Hz, 1H, H8), 7.50 (t, JHH = 7.4 Hz, 1H, H7), 7.91 (t,
JHH = 8.1 Hz, 1H, H6), 8.02 (br, 2H, H3 + H4), 8.21 (d, JHH = 8.0 Hz,
1H, H5). IR (KBr): 1084, 1032 (BF4) cmꢁ1. Yield of 6: 87 mg, 85%. A-
nal. Calc. for C, 44.46; H, 2.36; N, 5.46. Found: C, 44.18; H, 2.71; N,
5.08%. 1H NMR (CDCl3): d 7.31 (m, 1H, H8 + CDCl3), 7.56 (t, JHH = 8 Hz,
1H, H7), 7.91 (t, JHH = 8.3 Hz, 1H, H6), 8.01 (d, JHH = 5.7 Hz, 1H, H4),
8.10 (d, JHH = 8.3 Hz, 1H, H5), 8.31 (d, JHH = 5.7 Hz, 1H, H3). 19F NMR
(CDCl3): d ꢁ78.3 (s). 1H NMR (d6-acetone): d 7.45 (d, JHH = 8.3 Hz,
1H, H8), 7.67 (t, JHH = 7.9 Hz, 1H, H7), 8.01 (t, JHH = 7.8 Hz, 1H, H6),
8.32 (d, JHH = 8.3 Hz, 1H, H5), 8.35 (d, JHH = 5.7 Hz, 1H, H4), 8.52 (d,
JHH = 5.7 Hz, 1H, H3). 1H NMR (ꢁ55 °C, d6-acetone): d 7.57 (d,
JHH = 8.5 Hz, 1H, H8), 7.74 (t, JHH = 7.3 Hz, 1H, H7), 8.1 (t, JHH = 7.1 Hz,
1H, H6), 8.44 (d, JHH = 8.3 Hz, 1H, H5), 8.53 (d, JHH = 6.0 Hz, 1H, H4),
8.58 (d, JHH = 6.0 Hz, 1H, H3). IR (KBr): 1252, 638 (CF3SO3) cmꢁ1. Yield
of 7: 70 mg, 78%. Anal. Calc. for C, 47.94; H, 2.68; N, 6.21. Found: C,
47.65; H, 3.07; N, 6.13% N. 1H NMR (CDCl3): d 7.26 (H8 under CDCl3),
7.47 (t, JHH = 8.1 Hz, 1H, H7), 7.80 (t, JHH = 7.4 Hz, 1H, H6), 7.87 (brs,
1H, H4), 7.99 (d, JHH = 8.1 Hz, 1H, H5), 8.29 (brs, 1H, H3). 19F NMR
(CDCl3): d ꢁ153.1 (s). 1H NMR (d6-acetone): d 7.50 (d, JHH = 8.6 Hz,
1H, H8), 7.7 (t, JHH = 7.4 Hz, 1H, H7), 8.03 (t, JHH = 7.4 Hz, 1H, H6),
8.34 (d, JHH = 8.3 Hz, 1H, H5), 8.37 (d, JHH = 6.2 Hz, 1H, H4), 8.53 (d,
JHH = 6.2 Hz, 1H, H3). 1H NMR (ꢁ55 °C, d6-acetone): d 7.57 (d,
JHH = 8.6 Hz, 1H, H8), 7.74 (t, JHH = 7.1 Hz, 1H, H7), 8.1 (t, JHH = 7.3 Hz,
1H, H6), 8.43 (d, JHH = 8.6 Hz, 1H, H5), 8.53 (br, 2H, H4 + H3). IR (KBr):
1
d ꢁ78.1 (s). 31P{1H} NMR (CDCl3): d 14.9 (d, JAg–P = 687.7 Hz).
1
31P{1H} NMR (ꢁ55 °C, CDCl3):
d
12.1 (d, J109Ag–P = 760.1 Hz,
1J107Ag–P = 669.8 Hz). IR (KBr): 1288, 1241, 636 (CF3SO3) cmꢁ1. Yield
of 4: 81 mg, 69%. Anal. Calc. for C, 47.2; H, 3.27; N, 2.39. Found: C,
46.88; H, 3.24; N, 2.25%. 1H NMR (CDCl3): d 1.75 (d, JHP = 6.6 Hz, 6H,
Me), 7.13–7.46 (m, 20H, Ph), 7.51 (d, JHH = 8.3 Hz, 2H, H8), 7.59
(t, JHH = 8.7 Hz, 2H, H7), 7.75 (t, JHH = 7.8 Hz, 2H, H6), 7.82 (d,
JHH = 6.2 Hz, 2H, H4), 7.85 (d, JHH = 8.3 Hz, 2H, H5), 8.85 (d,
JHH = 6.2 Hz, 2H, H3). 1H NMR (ꢁ55 °C, CDCl3): d 1.57 (brs, 6H,
Me), 6.91–7.45 (m, 22H, Ph + H8), 7.61 (t, JHH = 7.5 Hz, 2H, H7),
7.71 (d, JHH = 6.1 Hz, 2H, H4), 7.82 (m, 4H, H5 + H6), 8.85 (d,
JHH = 6.1 Hz, 2H, H3). 19F NMR (CDCl3): d ꢁ78.0 (s). 31P{1H} NMR
(CDCl3): d ꢁ3.5 (br). 31P{1H} NMR (ꢁ55 °C, CDCl3): d ꢁ4.6 (d,
1J109Ag–P = 786.2 Hz, J107Ag–P = 681.8 Hz). IR (KBr): 1280, 1246,
1
638 (CF3SO3) cmꢁ1. Yield of 5: 86 mg, 80%. Anal. Calc. for C,
49.33; H, 3.58; N, 2.61. Found: C, 48.95; H, 3.46; N, 2.60%. 1H
NMR (CDCl3): d 1.79 (d, JHP = 7 Hz, 6H, Me), 7.08–7.46 (m, 20H,
Ph), 7.55 (d, JHH = 7.8 Hz, 2H, H8), 7.60 (t, JHH = 7.8 Hz, 2H, H7),
7.76 (t, JHH = 7.8 Hz, 2H, H6), 7.85 (d, JHH = 6.2 Hz, 2H, H4), 7.86 (d,
JHH = 8.7 Hz, 2H, H5), 8.85 (d, JHH = 6.2 Hz, 2H, H3). 1H NMR
(ꢁ55 °C, CDCl3): d 1.72 (brs, 6H, Me), 6.92–7.44 (m, 20H, Ph),
7.53 (d, JHH = 7.9 Hz, 2H, H8), 7.61 (t, JHH = 8 Hz, 2H, H7), 7.77 (t,
JHH = 8 Hz, 2H, H6), 7.85 (br, 2H, H5 + H4), 8.80 (br, 2H, H3). 19F
1
NMR (CDCl3): d ꢁ78.3 (s). 31P{1H} NMR (CDCl3): d ꢁ3.0 (d, JAg–
1
P = 717.8 Hz). 31P{1H} NMR (ꢁ55 °C, CDCl3): d ꢁ2.9 (d, J109Ag–
1
P = 789.9 Hz, J107Ag–P = 691.3 Hz). IR (KBr): 1098, 621 (ClO4) cmꢁ1
.
2.3. Synthesis of [(
R = Me, R0 = Ph (9). X = CF3SO3, R = Me, R0 = Ph (10)
l
-biisoq)2{AgX(PRR02)}2], X = ClO4; R = R0 = Ph (8),
To a dichloromethane solution(20 mL) of [AgX(PRR02)] (0.1 mmol;
X = ClO4, R = R0 = Ph 47 mg, R = Me, R0 = Ph 41 mg X = CF3SO3, R = Me,
R0 = Ph 46 mg,) was added biisoquinoline (0.1 mmol, 26 mg). The
mixture was stirred for 1 h protected from the light. The solution
was concentrated to ca. 5 mL. The addition of diethyl ether afforded
compounds as white off (8) or light yellow (9–10) solids. A second
fraction was obtained by concentration and addition of hexane.
Yield of 8: 47 mg, 65%. Anal. Calc. for C, 59.56; H, 3.75; N, 3.86. Found:
C, 59.81; H, 3.83; N, 3.92%. 1H NMR (CDCl3): d 7.05–7.44 (m, 30H, Ph),
7.47 (t, JHH = 7.6 Hz, 4H, H7), 7.58 (d, JHH = 7.6 Hz, 4H, H8), 7.75 (t,
JHH = 7.9 Hz, 4H, H6), 7.88 (d, JHH = 6.2 Hz, 4H, H4), 7.97 (d,
JHH = 8.3 Hz, 4H, H5), 8.55 (d, JHH = 6.2 Hz, 4H, H3). 1H NMR
(ꢁ55 °C, CDCl3): d 6.84–7.75 (brm, 50H, Ph + H4–8), 8.25 (brs, 4H,
H3). 19F NMR (CDCl3): d ꢁ78.1 (s). 31P{1H} NMR (CDCl3): d 15.1 (d,
1
1JAg–P = 692 Hz). 31P{1H} NMR (ꢁ55 °C, CDCl3): d 14.8 (d, J109Ag–
1
P = 717 Hz, J107Ag–P = 621.8 Hz). IR (KBr): 1096, 622 (ClO4) cmꢁ1
.
Yield of 9: 41 mg, 61%. Anal. Calc. for C, 56.09; H, 3.80; N, 4.22. Found:
C, 55.98; H, 3.95; N, 4.35%. 1H NMR (CDCl3): d 1.86 (d, JHP = 6.6 Hz,
6H, Me), 7.22–7.41 (m, 20H, Ph), 7.49 (t, JHH = 7.6 Hz, 4H, H7), 7.55
(d, JHH = 7.9 Hz, 4H, H8), 7.75 (t, JHH = 7.6 Hz, 4H, H6), 7.88 (d,
JHH = 5.7 Hz, 4H, H4), 7.95 (d, JHH = 8.3 Hz, 4H, H5), 8.64 (d,
JHH = 5.7 Hz, 4H, H3). 1H NMR (ꢁ55 °C, CDCl3): d 1.74 (brs, 6H, Me),
7.0–8.01 (brm, 40H, Ph + H4–8), 8.39 (brs, 4H, H3). 19F NMR (CDCl3):
d ꢁ78.2 (s). 31P{1H} NMR (CDCl3): d ꢁ3.6 (br). 31P{1H} NMR (ꢁ55 °C,
1084, 1034 (BF4) cmꢁ1
.
2.2. Synthesis of [(
R = Me, R0 = Ph (4). X = ClO4, R = Me, R0 = Ph (5)
l
-biisoq){AgX(PRR02)}2], X = CF3SO3; R = R0 = Ph (3),
To
(0.2 mmol; X = CF3SO3, R = R0 = Ph 104 mg, R = Me, R0 = Ph 91 mg,
a
dichloromethane solution (20 mL) of [AgX(PRR02)]

M. Bardají et al. / Inorganica Chimica Acta 386 (2012) 93–101
95
1
1
CDCl3): d ꢁ4.1 (d, J109Ag–P = 729 Hz, J107Ag–P = 628.4 Hz). IR (KBr):
1077, 622 (ClO4) cmꢁ1. Yield of 10: 50 mg, 70%. Anal. Calc. for C,
53.87; H, 3.53; N, 3.93. Found: C, 53.58; H, 3.55; N, 3.90%. 1H NMR
(CDCl3): d 1.77 (d, JHP = 7 Hz, 6H, Me), 7.11–7.44 (m, 20H, Ph), 7.52
(t, JHH = 7.5 Hz, 4H, H7), 7.57 (d, JHH = 7.9 Hz, 4H, H8), 7.75 (t,
JHH = 7.6 Hz, 4H, H6), 7.86 (d, JHH = 5.7 Hz, 4H, H4), 7.93 (d,
JHH = 8.3 Hz, 4H, H5), 8.70 (d, JHH = 5.7 Hz, 4H, H3). 1H NMR
(ꢁ55 °C, CDCl3): d 1.59 (brs, 6H, Me), 6.92–7.97 (brm, 40H,
Ph + H4–8), 8.54 (brs, 4H, H3). 19F NMR (CDCl3): d ꢁ78.2 (s). 31P{1H}
NMR (CDCl3): d ꢁ3.5 (br). 31P{1H} NMR (ꢁ55 °C, CDCl3): d ꢁ4.4 (d,
1J109Ag–P = 758.2 Hz, 1J107Ag–P = 650.1 Hz). IR (KBr): 1280, 1256, 637
anion of dimer 6b. Polymer 6c: silver centres occupy special
positions with 0.5 occupancies. Coordinated water in 3a and
6c: H of water were localized in Fourier maps, then the water
molecule was refined as a rigid unit. The diffraction intensity
of crystal 8a was low, but it was the best we could get. In com-
pound 10 the dichloromethane crystallization molecule was fixed
because of disorder.
3. Results and discussion
(CF3SO3) cmꢁ1
.
3.1. Synthesis and structural characterization
2.4. Crystal structure determination of compounds 3a, 6a, 6b, 6c, 8a, 9
and 10
The reaction of different silver(I) compounds with 1,10-biiso-
quinoline in different ratios gave rise to the structural types gath-
ered in Scheme 1.
The crystal was mounted on a glass fiber and transferred to
the Bruker SMART CCD or SuperNova Oxford Diffraction diffrac-
tometers. Crystal data and details of data collection and structure
refinement are given in Tables 1 and 2. Cell parameters were
retrieved using SMART [11] software and refined with SAINT
[12] on all observed reflections. Data reduction was performed
with the SAINT software and corrected for Lorentz and polariza-
tion effects. Absorption corrections were based on multiple scans
(program SADABS) [13]. For the SuperNova diffractometer was
used the CrysAlis system software [14]. The structure was refined
anisotropically on F2 [15]. All non-hydrogen atomic positions
were located in difference Fourier maps and refined anisotropi-
cally. The hydrogen atoms were placed in their geometrically
generated positions. The chloroform molecule of monocrystal
3a is ‘incipiently’ disordered. Triflate anion of dimer 6a was dis-
ordered: two CF3 were used and refined to be 65% and 35%,
respectively; the majority was used in Fig. 6. There is some
disorder in the coordinated acetone molecule and in the triflate
The silver salts Ag(CF3SO3) and Ag(BF4) react with 1,10-biisoquin-
oline in 1:2 M ratio yielding [Ag(biisoq)2]nXn (1: X = CF3SO3; 2:
X = BF4). Compounds1 and 2 are air-stable white solids at room tem-
perature, and were characterized by elemental analysis, IR and NMR
spectroscopy. In their 1H NMR spectra, the aromatic biisoquinoline
protonsH3 and H8 are slightlyhigh-fieldshifted compared to the free
ligand, whilst H4–7 are slightly high- or low-field shifted depending
on the compound (see Section 2). The largest shifts are 0.32–
0.58 ppm for H3 and 0.24–0.39 ppm for H8. The 1H NMR spectra
show only one kind of isoquinoline unit even at low temperature
(ꢁ55 °C), which points out to symmetric coordination for the 1,10-
biisoquinoline ligand. The 19F NMR spectra show a singlet at ꢁ78.3
or ꢁ153 ppm, due to the triflate or tetrafluoroborate anion. The
compounds are poorly soluble in acetone, chloroform or dichloro-
methane, and insoluble in hexane or diethyl ether. Crystals of com-
pounds 1–2 suitable for X-ray diffraction could not be obtained.
Related derivatives with planar 2,20-bipyridine type ligands and
several anions are mononuclear [16]. The higher flexibility of
Table 1
Details of crystal data and structure refinement for complexes 3a, 6a–c.
Compound
3aÅCHCl3
6a
6b
6c
Empirical formula
fw
T (K)
C
57H45Ag2Cl3F6N2O7P2S2
C50H48Ag2F6N4O10S2
1258.78
298(2)
C44H36Ag2F6N4O8S2
1142.63
298(2)
C19H14AgF3N2O4S
531.25
298(2)
1432.10
298(2)
Wavelength (Å)
Crystal system
Space group
Unit cell dimension
a (Å)
0.71073
triclinic
P1
0.71073
monoclinic
C2/c
0.71073
orthorhombic
Pbcn
0.71073
monoclinic
C2/c
ꢀ
14.2337(5)
14.2910(6)
15.8288(5)
68.190(4)
14.8433(5)
19.8286(4)
19.9058(7)
90
13.0336(3)
17.9025(3)
20.0081(4)
90
19.8010(6)
9.7134(3)
21.1092(6)
90
b (Å)
c (Å)
a
(°)
b (°)
81.252(3)
85.340(3)
2953.49(19)
2
1.610
110.999(4)
90
5469.6(3)
90
90
107.643(3)
90
3869.0(2)
v
(°)
V (Å3)
4668.59(16)
4
1.626
1.008
2288
Z
4
8
Dcalc (Mg/m3)
1.529
0.870
2544
1.824
1.208
2112
Absorption coefficient (mmꢁ1
F(000)
)
0.995
1436
Crystal habit
prism
prism
plate
prism
Crystal size (mm)
0.38 ꢂ 0.14 ꢂ 0.11
2.82–28.78
ꢁ19 ꢃ h ꢃ 19
ꢁ19 ꢃ k ꢃ 19
ꢁ21 ꢃ l ꢃ 21
19965
0.37 ꢂ 0.30 ꢂ 0.20
2.94–28.82
ꢁ19 ꢃ h ꢃ 18
ꢁ26 ꢃ k ꢃ 25
ꢁ18 ꢃ l ꢃ 26
10632
0.36 ꢂ 0.20 ꢂ 0.09
2.81–28.83
ꢁ17 ꢃ h ꢃ 17
ꢁ24 ꢃ k ꢃ 24
ꢁ27 ꢃ l ꢃ 27
11843
0.39 ꢂ 0.19 ꢂ 0.18
2.89–28.81
ꢁ17 ꢃ h ꢃ 26
ꢁ10 ꢃ k ꢃ 12
ꢁ26 ꢃ l ꢃ 27
7555
H
range for data collection
Index ranges
Reflections collected
Independent reflections
12223 [Rint = 0.0210]
0.966 and 0.916
12223/0/729
0.971
5713 [Rint = 0.0216]
0.864 and 0.597
5713/0/375
0.994
4979 [Rint = 0.0214]
0.992 and 0.980
4979/0/298
0.932
4063 [Rint = 0.0226]
1.00000 and 0.76569
4063/0/272
1.034
Maximum and minimum transition
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0471, wR2 = 0.1228
R1 = 0.0780, wR2 = 0.1339
0.922 and ꢁ0.972
R1 = 0.0455, wR2 = 0.1275
R1 = 0.0718, wR2 = 0.1370
0.750 and ꢁ0.655
R1 = 0.0388, wR2 = 0.1108
R1 = 0.0675, wR2 = 0.1178
0.590 and ꢁ0.422
R1 = 0.0338, wR2 = 0.0858
R1 = 0.0464, wR2 = 0.0897
0.592 and ꢁ0.502
Largest difference in peak hole (e Åꢁ3
)

96
M. Bardají et al. / Inorganica Chimica Acta 386 (2012) 93–101
Table 2
Details of crystal data and structure refinement for complexes 8a, 9 and 10.
Compound
8a
9Å(CH2Cl2)2
10Å(CH2Cl2)2
Empirical formula
fw
C81H72Ag2Cl2N4O11P2
1626.01
C64H54Ag2Cl6N4O8P2
1142.63
C66H54Ag2Cl4F6N4O6P2S2
1596.73
T (K)
298(2)
298(2)
298(2)
Wavelength (Å)
Crystal system
Space group
Unit cell dimension
a (Å)
0.71073
0.71073
0.71073
monoclinic
P 21/c
triclinic
triclinic
ꢀ
ꢀ
P1
P1
14.4358(12)
14.6764(10)
20.5851(19)
104.042(7)
12.4994(7)
12.6733(8)
12.7547(6)
73.762(5)
13.5878(8)
21.7748(14)
12.5713(7)
90
b (Å)
c (Å)
a
(°)
b (°)
105.431(8)
105.840(7)
3803.5(5)
2
1.420
0.689
1664
61.149(6)
65.462(6)
1601.86(16)
1
1.552
110.516(7)
90
3483.6(4)
v
(°)
V (Å3)
Z
2
Dcalc (Mg/m3)
1.522
0.889
1608
Absorption coefficient (mmꢁ1
F(000)
)
0.969
756
Crystal habit
prism
prism
prism
Crystal size (mm)
0.35 ꢂ 0.19 ꢂ 0.11
2.90–28.69
ꢁ15 ꢃ h ꢃ 18
ꢁ18 ꢃ k ꢃ 11
ꢁ26 ꢃ l ꢃ 25
16580
0.32 ꢂ 0.15 ꢂ 0.12
3.06–28.80°.
ꢁ16 ꢃ h ꢃ 16
ꢁ17 ꢃ k ꢃ 17
ꢁ17 ꢃ l ꢃ 17
10747
0.35 ꢂ 0.26 ꢂ 0.15
2.89–28.64
ꢁ17 ꢃ h ꢃ 12
ꢁ18 ꢃ k ꢃ 28
ꢁ14 ꢃ l ꢃ 16
13966
H
range for data collection
Index ranges
Reflections collected
Independent reflections
13157 [Rint = 0.0201]
0.963 and 0.884
13157/0/925
1.017
6648 [Rint = 0.0350]
0.899 and 0.797
6648/0/389
0.950
7306 [Rint = 0.0346]
0.914 and 0.847
7306/3/416
1.045
Maximum and minimum transition
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0495, wR2 = 0.1256
R1 = 0.0876, wR2 = 0.1395
0.750 and ꢁ0.482
R1 = 0.0576, wR2 = 0.1475
R1 = 0.1029, wR2 = 0.1645
1.346 and ꢁ0.780
R1 = 0.0609, wR2 = 0.1762
R1 = 0.0888, wR2 = 0.1860
1.074 and ꢁ0.665
Largest difference in peak hole (e Åꢁ3
)
p
conductivity) vs. c (c = equivalent concentration) in MeNO2 for 1
is ꢁ2200, supporting a 4:1 or higher electrolyte; for 2 the slope is
ꢁ600, suggesting values of oligomerization between 2:1 and 3:1
[17]. For the structure in the solid state there is only indirect support,
but a polymeric structure, as found in solution would also explain
betterthe low solubility of the compounds. Moreover, as seen below,
all the structures found here contain bridging biisoquinoline, not
chelating biisoquinoline. Overall, all that indirect evidence seems
to be compatible with an oligomeric structure for 1–2 also in the
solid state.
= Ag;
= AgXL;
= AgL2
7
6
3
5
4
8
1
=
N
N
N
N
N
biisoq:Ag
2:1
n+
X
N
N
X
Treatment of complexes [AgXL] with 1,10-biisoquinoline in
2:1 M ratio leads to dinuclear compounds 3–5 with a bridging biiso-
N
N
1:2
L
n
quinoline ligand [(l
-biisoq){AgX(PRR02)}2] (3: X = OSO2CF3, L = PPh3;
N
L
4: X = OSO2CF3, L = PMePh2; 5: X = OClO3, L = PMePh2). Compounds
3–5 are air-stable white solids at room temperature, and were char-
acterized by elemental analysis, IR, and NMR spectroscopy. Their
main features are: (a) the aromatic biisoquinoline protons are
slightly low-field (H6 and H7 for 3–5, H3 and H4 for 4–5) or high-
field (H5 and H8 for 3–5, H3 and H4 for 3) shifted, the largest shifts
values being 0.15–0.20 ppm for H8; (b) the 1H NMR spectra at
ꢁ55 °C show only one kind of isoquinoline half; (c) the integrations
confirm a 1:2 M ratio of the two kinds of ligand; (d) a singlet in the
19F NMR spectra in 3 and 4 corresponds to the triflate anion; (e) a
broad resonance for the coordinated phosphine, due to unresolved
3-5
1, 2
n+
N
N
N
N
N
N
N
N
N
1:1
N
N
N
N
n
6a, 6b, 7
8-10
6c
Scheme 1. Structural types of Ag(I) complexes with 1,10-biisoquinoline.
A
B
+
n+
N
N
N
N
1,10-biisoquinoline might produce the same kind of structure data
(structure A in Fig. 1), or alternatively give rise to oligomeric or poly-
meric species (structure B in Fig. 1), compatible with the previous
data. In fact, the values of molar conductivity at different concentra-
tions do not correspond to a 1:1 electrolyte, but support oligomeri-
zation in solution. Thus, the slope of the plot of Ke (equivalent
N
N
N
N
n
Fig. 1. Alternative bonding modes of 1,10-biisoquinoline in 1–2.

M. Bardají et al. / Inorganica Chimica Acta 386 (2012) 93–101
97
coupling to the two silver isotopes, was observed in the 31P{1H}
Table 3
Selected bond lengths [Å] and angles [°] for complex 3a.
NMR spectra; the two Ag–P couplings are resolved at low temper-
ature (ꢁ55 °C), where two doublets are observed centred at
3a
1
12.1 ppm (1J109Ag–P = 760.1 Hz, J107Ag–P = 669.8 Hz) for complex 3,
Ag(1)–N(1)
Ag(1)–P(1)
Ag(1)–O(1) water
N(1)–C(1)
N(1)–C(9)
Ag(2)–N(2)
Ag(2)–P(2)
Ag(2)–O(2) triflate
N(2)–C(10)
N(2)–C(18)
N(1)–Ag(1)–P(1)
N(1)–Ag(1)–O(1)
P(1)–Ag(1)–O(1)
C(1)–N(1)–C(9)
C(1)–N(1)–Ag(1)
C(9)–N(1)–Ag(1)
N(2)–Ag(2)–P(2)
N(2)–Ag(2)–O(2)
P(2)–Ag(2)–O(2)
C(10)–N(2)–C(18)
C(10)–N(2)–Ag(2)
C(18)–N(2)–Ag(2)
2.292(3)
2.3746(9)
2.3963
ꢁ4.6 (1J109Ag–P = 786.2 Hz, 1J107Ag–P = 681.8 Hz) for 4, and
ꢁ2.9 ppm (d, 1J109Ag–P = 789.9 Hz, 1J107Ag–P = 691.3 Hz) for 5.
The solid-state structure of a derivative of 3 was solved by
single-crystal X-ray diffraction studies. The crystal studied was ob-
tained by slow diffusion of hexane into a solution of 3 in chloro-
1.330(4)
1.361(5)
2.208(3)
2.3597(12)
2.533(3)
1.321(4)
1.376(5)
141.93(7)
87.27(7)
130.71(4)
118.1(3)
119.8(2)
121.9(2)
153.50(8)
93.35(13)
111.45(11)
117.8(3)
120.5(2)
121.6(2)
ꢀ
form at ꢁ18 °C. The compound crystallized in the P1 space
group, and the asymmetric unit contained one molecule. Unex-
pectedly, the molecule was non-symmetric and corresponded to
the formula [(l-biisoq){Ag(OSO2CF3)(PPh3)}{Ag(OH2)(PPh3)}](CF3-
SO3), labeled as 3a. The molecular structure of the cation is shown
in Fig. 2, with selected bond lengths and angles in Table 3, and dis-
plays the expected dinuclear structure with a bridging biisoquino-
line. There are two different silver centres; both are tricoordinated
by the bridging biisoquinoline, the phosphine, and an oxygen atom
from one triflate anion or a water molecule, respectively. Each sil-
ver atom displays a highly distorted trigonal geometry, with large
P–Au–N angles of 141.93(7)° and 153.50(8)°, and small N–Ag–O
angles of 87.27(7)° and 93.35(13)°. The Ag–N distances are
2.292(3) and 2.208(3) Å, while the Ag–O distances are 2.3963 (for
the water) and 2.533(3) Å (for triflate). The biisoquinoline ligand
displays a torsional angle NCCN of 113.1°, which produces a long
intramolecular silver–silver distance (5.157 Å) precluding any
AgꢀꢀꢀAg interaction. The shortest nonbonding intermolecular Ag–
Ag distance is 7.660 Å. We have not found related X-ray structures
for 2,20-bypiridine-type ligands. Apparently the compound studied
was formed by reaction of 3 with adventitious water during crys-
tallization. It is not unreasonable to think that the structure of
complex 3 might be related to that of 3a, but with a second coor-
dinated triflate in the place of water, as water is not observed in the
IR spectrum.
confirm the 1:1 biisoquinoline:phosphine molar ratio. The biiso-
quinoline protons H3 and H8 are slightly high-field shifted, whilst
H4 is low-field shifted. A singlet around ꢁ78 ppm is observed in
the 19F NMR spectra due to the triflate anion. Finally, the 31P{1H}
NMR spectra show a broad resonance at ca. 15 or ꢁ3.5 ppm, respec-
tively, for the coordinated PPh3 or PPh2Me coupled to the two silver
isotopes. The two doublets due to Ag–P coupling are seen at low
1
temperature (ꢁ55 °C) at 14.8 (1J109Ag–P = 717 Hz, J107Ag–P
=
621.8 Hz) for 8, ꢁ4.1 (1J109Ag–P = 729 Hz, 1J107Ag–P = 628.4 Hz) for 9,
and ꢁ4.4 (1J109Ag–P = 758.2 Hz, 1J107Ag–P = 650.1 Hz) ppm for 10.
The dinuclear structures of 8–10 were solved by single-crystal
X-ray diffraction studies and confirmed the bridging coordination
of the ligand biisoquinoline. The molecules are shown in
Figs. 3–5, with selected bond lengths and angles in Table 4. Com-
The most interesting structures were produced in the reactions
using Ag:biisoquinoline = 1:1 ratio. Depending on the ancillary li-
gands and other conditions, three structural types were found. As
discussed below, the three types display bridging coordination of
the 1,10-biisoquinoline ligand.
ꢀ
pounds 8 and 9 crystallize in the triclinic P1 space group, and com-
The reaction of biisoquinoline with [AgXL] (X = ClO4, CF3SO3;
L = phosphine) complexes in a 1:1 M ratio, led to the corresponding
phosphine/biisoquinoline compounds [(l-biisoq)2{AgXL}2] 8–10
(Scheme 1; 8: X = OClO3, L = PPh3; 9: X = OClO3, L = PMePh2; 10:
X = OSO2CF3, L = PMePh2). Compounds 8–10 are air-stable pale
yellow solids at room temperature, and were characterized by
elemental analysis, IR, and NMR spectroscopy. The 1H NMR spectra
pound 10 in the monoclinic P21/c space group. The crystal obtained
by slow diffusion of hexane into an acetone solution of 8 at ꢁ18 °C,
displayed two independent molecules with slightly different dis-
tances and angles, and showed that acetone had displaced perchlo-
rate as ligand during crystallization producing a ionic derivative of
8, with formula [(l-biisoq)2{Ag(acetone)(PPh3)}2](ClO4)2, labeled as
8a. This is not the case of the crystals of 9 and 10, crystallized by
slow diffusion of hexane into an acetone/dichloromethane solution
of 9 or by slow diffusion of diethyl ether/tetrahydrofurane into a
dichloromethane solution of 10, both at ꢁ18 °C, which show neu-
tral dinuclear molecules with perchlorate or triflate coordinated
to silver.
The three structures have many features in common. Each silver
atom is tetracoordinated, and is bonded to two different biisoquin-
oline bridging ligands, to the corresponding phosphine (PPh3 for
8a, PPh2Me for 9 and 10), and to an oxygen donor atom from
acetone (8a), perchlorate (9) or triflate (10). This coordination gives
rise to a 10-membered metallacycle containing four N and two Ag
atoms. The small differences in the metallic fragment lead to tor-
sional NCCN angles in the biisoquinoline of 100.3 (94.5° for the sec-
ond molecule) for 8a, 79.7° for 9, 98.9° for 10, and therefore, to
different intramolecular Ag–Ag distances: 4.070 Å (4.434 Å for
the second molecule) for 8a), 3.684 Å for 9), and 4.392 Å for 10).
These Ag–Ag distances are clearly longer than accepted for argent-
ophilic interactions (2.88–3.44 Å). The silver atoms display a highly
distorted tetrahedral geometry, with larger N–Ag–P angles (in the
range 125.23(10)°–138.41(11)°) and smaller N–Ag–O (in the range
Fig. 2. Structure of the cation [(l
-biisoq){Ag(OSO2CF3)(PPh3)}{Ag(OH2)(PPh3)}]+
(3a), derived from 3. Displacement ellipsoids are at 20% probability level (H atoms
omitted for clarity).

98
M. Bardají et al. / Inorganica Chimica Acta 386 (2012) 93–101
Fig. 3. Structure of the cation of compound 8a. Ellipsoids are at 20% probability
level (H atoms omitted for clarity).
Fig. 5. Structure of compound 10. Ellipsoids are at 20% probability level (H atoms
omitted for clarity).
Fig. 4. Structure of compound 9. Ellipsoids are at 20% probability level (H atoms
omitted for clarity).
82.82(19)°–92.55 (16)°) and N–Ag–N angles (in the range
90.46(14)°–97.93(14)°), as observed in structure of 3a. All the Ag–
N distances are very similar, in the range 2.304(4)–2.353(4) Å, and
are longer than those found in 3a for tricoordinated silver
(2.208(3) and 2.292(3) Å). The Ag–P distances, in the range
2.3705(14)–2.3849(13) Å, are similar to or slightly longer than those
found for 3a (2.3597(12) and 2.3746(9) Å). The Ag–O distances of
2.746(4) and 2.819(4) Å for compound 8a (acetone), 2.736(5) Å for
compound 9 (perchlorate) and 2.758(4) Å for compound 10 (tri-
flate), are much longer than observed in compound 3a (2.3963 and
2.553 Å). The biisoquinoline ligand displays the expected distances
Fig. 6. Structure of the dimeric molecule of compound 6a. Ellipsoids are at 20%
probability level (H atoms and acetone of crystallization omitted for clarity).
Table 4
Selected bond lengths [Å] and angles [°] for complexes 8a (two inequivalent
molecules), 9 and 10.
8a
8a (2nd mol)
9
10
Ag–N
2.333(3)
2.347(4)
2.3772(12) 2.3796(12)
2.746(4)
(acetone)
1.360(6)
1.325(6)
2.304(4)
2.346(3)
2.326(4)
2.353(4)
2.3849(13)
2.736(5)
(perchlor.)
1.315(6)
1.372(6)
97.73(14)
2.314(4)
2.350(4)
2.3705(14)
2.758(4)
(triflate)
1.382(7)
1.315(6)
91.68(16)
Ag–P
Ag–O
and angles. In addition there is
p–p stacking between the C2–C7
2.819(4)
(acetone)
1.318(5)
1.372(6)
93.42(13)
biisoquinoline ring and a phenyl phosphine ring: several C–C dis-
tances in the range 3.53–3.71, 3.52–3.76 and 3.43–3.73 Å are found,
respectively, for compounds 8a, 9 and 10.
N–C
N–Ag–N 90.46(14)
Related silver compounds with 2,20-bypiridine-type ligands and
phosphines in AgX:phosphine:N,N-ligand 1:1:1 ratio are well-
studied and characterized. In all the cases they yield mononuclear
compounds with a chelate N,N-ligand, and the coordination sphere
is completed with the phosphine, and sometimes with the anion
[18]. In contrast, the 1,10-biisoquinoline ligand shows high prefer-
ence to act as a bridging ligand in a dimer.
N–Ag–P
138.41(11) 134.34(10)
130.96(10) 131.60(10)
136.63(10)125.23(10) 135.84(12)
132.45(11)
N–Ag–O 91.71(12)
85.80(14)
89.36(14)
84.72(13)
88.03(10)
117.7(4)
117.7(4)
82.82(19)
92.55(16)
99.22(16)
117.7(4)
117.5(4)
87.75(15)
89.20(15)
93.67(12)
117.2(5)
117.5(5)
P–Ag–O
C–N–C
88.48(9)
118.8(4)
117.8(4)

M. Bardají et al. / Inorganica Chimica Acta 386 (2012) 93–101
99
Finally, the reactions of the silver salts Ag(CF3SO3) and Ag(BF4)
with 1,10-biisoquinoline in 1:1 M ratio yield apparently simple
compounds of stoichiometry [AgX(biisoq)] (6: X = CF3SO3; 7:
X = BF4). Compounds 6 and 7 are air-stable white solids at room
temperature, and were characterized by elemental analysis, IR
and NMR spectroscopy. They are poorly soluble in acetone, chloro-
form or dichloromethane, and insoluble in hexane or diethyl ether.
In their 1H NMR spectra, the aromatic biisoquinoline protons H3
and H8 are slightly high-field shifted by comparison to the free
ligand, whilst H4–7 are slightly high or low-field shifted depending
on the compound (see Section 2). The biggest shifts are 0.32–
0.58 ppm for H3 and 0.24–0.39 ppm for H8. Even the 1H NMR spec-
tra at low temperature (ꢁ55 °C) show only one kind of isoquinoline
unit, which points out to symmetric coordination for the 1,10-biiso-
quinoline ligand. The 19F NMR spectra show a singlet at ꢁ78.3 or
ꢁ153 ppm due to the triflate or tetrafluoroborate anion.
tone)}2]ꢀ2acetone and crystallizes in the monoclinic C2/c system; the
other, denoted 6b, is [( -biisoq)2{Ag(OSO2CF3)(acetone)}2] and
l
crystallizes in the orthorhombic Pbcn system. Their main difference
is that the monoclinic polymorph is solvated with two molecules of
acetone per dimer; this crystallization acetone is lost easily, often
cracking the crystals. The structures were established by X-ray
diffraction. In both cases, the asymmetric unit is half of the molecule.
The molecule is shown in Fig. 6, with selected bond lengths and an-
gles in Table 5.
Compounds 6a and 6b are dimers, with two tetracoordinated
silver(I) centres in a highly distorted tetrahedral arrangement
and a double biisoquinoline bridge between them. Each silver cen-
tre is bonded to two N-donor atoms of the biisoquinoline ligands,
and to two oxygens: one of the triflate anion, and the second of
an acetone molecule. Besides, the dimer displays a short intramo-
lecular AgꢀꢀꢀAg distance of 3.0737(6) or, respectively, 3.1358(6) Å
for 6a or 6b. The shortest intermolecular Ag–Ag distance is of
8.513 or, respectively, 9.573 Å, for 6a or 6b. Polynuclear molecular
compounds containing monovalent coinage metals show a remark-
able tendency to aggregation despite their formally closed-shell
d10 electronic configuration [19]. This behavior has been particu-
larly well documented for gold, but experimental and theoretical
evidence has also been reported for the analogous argentophilic
interaction [3]. Typically, Ag–Ag distances in the range 2.88 (metal-
lic distance) to 3.44 Å (sum of van der Waals radii) are indicative of
these interactions.
Crystals of 6, obtained by slow diffusion of diethyl ether in a solution
of acetone at ꢁ18 °C, showed two different polymorphs of the same
molecular structure. One, denoted 6a, is[(l-biisoq)2{Ag(OSO2CF3)(ace-
Table 5
Selected bond lengths [Å] and angles [°] for complexes 6a–c.
6a
6b
6c
Ag(1)–N(1)
2.277(3)
2.264(3)
2.553(7)
2.542(3)
2.285(3)
2.248(3)
2.399(3)
2.511(4)
2.231(2)
2.231(2)
–
Ag(1)–N(2)/N(1A)
Ag(1)–O(1) trif.
Ag(1)–O(4) acet.
Ag(1)–O(1) water
Ag(1)–Ag(1)#1
Ag(2)–N(2)
Ag(2)–N(2B)
N(1)–C(1)
N(1)–C(9)
N(2)–C(10)
Another structure related to 6, denoted as 6c, was crystallized
by slow diffusion of hexane in a solution of dichloromethane at
ꢁ18 °C. Again, the compound crystallizes in the monoclinic C2/c
space group. The molecular X-ray diffraction structure is shown
in Fig. 7, with selected bond lengths and angles in Table 5. Com-
–
–
–
2.5347
–
3.0737(6)
–
–
1.322(4)
1.378(5)
1.320(5)
1.369(5)
140.28(11)
–
–
105.69(11)
–
92.38(12)
–
3.1358(6)
–
–
1.309(4)
1.364(4)
1.316(4)
1.372(4)
141.85(11)
–
–
112.65(15)
–
90.28(15)
–
2.159(2)
2.159(2)
1.333(3)
1.370(3)
1.323(3)
1.376(4)
–
147.90(11)
180.00
–
99.00(5)
–
103.02(5)
–
103.03(5)
99.00(5)
–
pound 6c displays an asymmetric unit of formula [(
l-biisoq)A-
g(OH2)2( -biisoq)Ag]n(CF3SO3)2n. The asymmetric unit contains a
l
dinuclear fragment, with the silver atoms in 0.5 occupancies. In
this structure the biisoquinoline ligands act as a single-bridge (in-
stead of double-bridge) between silver atoms, which leads to a 1D
polymer instead of a dimer. One silver centre is tetracoordinated
with two N atoms of two different biisoquinoline ligands and
two water molecules. The second independent silver centre is only
linearly dicoordinated to two biisoquinoline ligands. There is no
Ag–Ag interaction. The 2.159(2) Å Ag–N distance in the 2-coordi-
nate silver centre, is clearly shorter than 2.231(2) Å in the 4-coor-
dinate silver centre; the later is in turn slightly shorter than
observed for 4-coordinate silver centres in the dimeric compounds
6a–b (2.248(3)–2.285(3) Å) or in compounds 8a–10 (2.304(4) to
2.353(4) Å). The Ag–O distances are quite similar, in the range
2.511(4)–2.553(7) Å, independently of the nature of the ligand
(acetone, triflate or water); only one Ag–O (triflate) distance of
2.399(3) Å for the unsolvated dimer is shorter. These distances
are similar to those found in 3a (2.3963 and 2.553 Å) and much
N(2)–C(18)
N(2)–Ag(1)–N(1)
N(1A)–Ag(1)–N(1)
N(2)–Ag(2)–N(2B)
N(2)–Ag(1)–O(4)
N(1A)–Ag(1)–O(1A)
N(1)–Ag(1)–O(4)
N(1)–Ag(1)–O(1A)
N(2)–Ag(1)–O(1)
N(1A)–Ag(1)–O(1)
N(1)–Ag(1)–O(1)
O(4)–Ag(1)–O(1)
O(1)–Ag(1)–O(1A)
C(1)–N(1)–C(9)
C(1)–N(1)–Ag(1)
C(9)–N(1)–Ag(1)
C(10)–N(2)–C(18)
C(10)–N(2)–Ag(2)
C(18)–N(2)–Ag(2)
127.43(15)
–
88.02(17)
86.3(2)
110.31(11)
–
94.77(11)
98.82(17)
–
–
92.7
118.2(3)
121.8(2)
119.7(2)
–
–
–
118.6(3)
121.4(2)
119.8(2)
–
–
–
118.5(2)
122.71(17)
118.78(17)
118.0(2)
123.78(18)
117.51(17)
Fig. 7. Polymeric structure of the cation of compound 6c (uncoordinated triflate anion omitted). Ellipsoids are at 50% probability level (H atoms omitted for clarity).

100
M. Bardají et al. / Inorganica Chimica Acta 386 (2012) 93–101
3.2. Photophysical studies
The absorption spectra of the compounds, as isolated in the
experimental part, were measured in dichloromethane in the range
200–600 nm. The detailed results are given as Supplementary
material (Table S1). The main features for the spectra of the gold
derivatives are, monotonically, the following: (1) an intense
absorption at 230–234 nm, due to phenyl rings [23]; (2) absorp-
tions around 266–278 nm, also related with the aromatic rings of
the biisoquinoline or phosphine ligands; (3) a broad peak with
intensity maxima in the range 331–338 nm, related to p–
p⁄ transi-
tions in the biisoquinoline ligand, but red-shifted after coordination
to silver(I), which can also be related to metal–ligand charge trans-
fer transitions.
The emission and excitation spectra of the free ligand and the
silver complexes were recorded in the solid-state and in CH2Cl2
solution, at 298 and 77 K. All the derivatives, including the free
1,10-biisoquinoline ligand, emit at 77 and 298 K in the solid state
and in solution. The detailed results are given in the Supplemen-
tary material (Tables S2 and S3). The spectra of compounds 6
and 10 in the solid state are shown in Fig. 8. All the derivatives,
including the free 1,10-biisoquinoline ligand, emit at 77 and
298 K in the solid state and in solution.
In the solid state, the emission maxima range goes from 397 to
519 nm at 298 K. Actually, compounds 1–7 (and the ligand) emit in
the short range 397–414 nm, whilst compounds 8–10 emit at
494–519 nm. At 77 K there are again two groups of emissive com-
pounds: the ligand and derivatives 1–7 show emission maxima
from 366 to 399 nm (up to 435 nm by considering lower intensity
emission spectra), and derivatives 8–10 emit at 468–523 nm.
Moreover, the emission spectra are more complex, and in some
cases a second (even a third for 8) less intense spectra can be ob-
served. The low temperature emission and excitation maxima
peaks are slightly blue shifted, except the emission for compound
10, which is slightly red shifted. The biisoquinoline ligand is lumi-
nescent, as expected from the presence of naphthalene-type units.
It is reasonable to assign the emission as ligand centred slightly
modified by the silver fragment for compounds 1–7. Dinuclear
derivatives 8–10 display a clearly different emission, red-shifted
around 100 nm, but the presence of vibronic progressions (1165–
1207 cmꢁ1, close to those found in the IR spectra for skeletal vibra-
tions in the biisoquinoline) suggests that biisoquinoline is partici-
pating in the transition. This emission could be tentatively
assigned as a metal to ligand charge-transfer transition [5d,5e].
All the compounds show emission maxima in CH2Cl2 solution at
298 K in the range 376–490 nm (495 nm taking into account lower
intensity emission spectra). Actually, there is an emission centred
at ca. 380 nm, and a second centred at 460 nm with a vibronic peak
at 490 nm (as observed for compounds 8 and 10 in the solid state
at 77 K). At low temperature, the emission range is shorter than ob-
served at room temperature and strongly blue-shifted: 376–
402 nm. The 77 K emission spectra are simpler: the peaks centred
at ca. 460 and 490 nm have disappeared, and all the derivatives show
spectra similar to the biisoquinoline spectrum. Therefore, the higher
energy emission can be tentatively assigned as ligand centred slightly
modified by the silver fragment, whilst the lower energy emission
could be related to a metal to ligand charge-transfer transition.
Fig. 8. Solid state excitation and emission spectra of compounds 6 (regular line)
and 10 (bold line): (a) at 298 K; (b) at 77 K.
shorter than those observed for 8a–10 (from 2.736(5) to
2.819(4) Å). The tetracoordinated silver centre shows the largest
N–Ag–N angle (140.28(11)–147.90(11)°), and the biisoquinoline li-
gand displays similar distances and angles in the three crystal
structures, although the torsional angles (NCCN) are different. This
angle is being larger for the polymer than for the dimers, as
expected from the geometry: 66.0° and 67.8° for 6a, 68.2 and
79.9° for 6b, and 111.8° for 6c.
It is interesting to compare these results with those obtained for
silver complexes with 2,20-bipyridine and related ligands. Mono-
nuclear derivatives have been reported with these N,N-ligands act-
ing as chelate and the coordinating sphere of silver bonded to the
anion and/or a coordinating solvent, for instance [Ag(CF3CO2)(bi-
py)], [Ag(ClO4)(bq)] (bq: 2,20-biquinolyl) and [Ag(NO3)(Me-bipy)]
(Me-bipy: 4,40-dimethyl-2,20-bipyridine [20,16c]. Also one-dimen-
sional polymers, with bridging N,N-ligand as in [Ag(ClO4)(bipy)], or
bridging anion as in [Ag(NO3)(bipy)], have been reported [20]. As
found for compound 6c, the coordination polymers derived from
silver ions and bipyridine-type ligands show a preference for
two-coordinate linear geometry silver centres, although they can
adopt higher coordination numbers [3d,4c,4f,20,21].
As for compound 7, we failed to obtain monocrystals for X-ray
diffraction study from different solvents. The IR spectrum of the
4. Conclusions
1,10-Biisoquinoline is an extraordinarily flexible and versatile
ligand. In the complexes reported here it always acts as bridging
ligand that can modify the Ag–Ag distance in dinuclear bridged
compounds by changing the torsion angle between the two iso-
quinoline subunits. We have found torsion angles in the range
66.0–79.9°, with intramolecular Ag–Ag short distances from
original preparation of 7 shows splitting of the m(B–F) band around
1050 cmꢁ1, indicating the existence of some kind of interaction or
coordination involving the anion, which that decreases the Td sym-
metry of the free anion [22]. In case of coordination, the solid state
structure would correspond to a neutral compound. However, with
only these data a specific structure cannot be proposed.

M. Bardají et al. / Inorganica Chimica Acta 386 (2012) 93–101
101
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3.0737(6) to 3.68 Å, for compounds 6a, 6b and 9; but also torsional
angles from 94.5° to 113.1° with intramolecular Ag–Ag large
distances in the range 4.070–5.157 Å, for compounds 3a, 8a and
10. The ligand can also form polymers as 6c with a torsional angle
of 111.8°. This flexibility induces a ligand response to the number
and steric requirements of the auxiliary ligands, the number of
bridging biisoquinoline ligands available per silver atom (one or
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We thank the Spanish Comisión Interministerial de Ciencia y
Tecnología (Project CTQ2011-25137 and Consolider Ingenio 2010,
INTECAT, CSD2006-0003) and the Junta de Castilla y León (Project
VA248A11-2) for financial support.
Appendix A. Supplementary material
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Supplementary material CCDC 856923–856929 contains the
supplementary crystallographic data for the complexes 3a, 6a,
6b, 6c, 8a, 9 and 10, respectively. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via
http://www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
associated with this article can be found, in the online version, at
doi:10.1016/j.ica.2012.01.059.
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