Metal-organophosphonate chemistry: Hydrothermal syntheses and structures of copper(II)-xylyldiphosphonates with organonitrogen coligands

Article abstract of DOI:10.1016/j.ica.2013.01.001

The hydrothermal reactions of copper(II) acetate monohydrate or copper(II) chloride dihydrate with xylyl-phosphonic acid derivatives in the presence of organonitrogen coligands yielded a series of compounds of the Cu(II)/ligand/xylyl-diphosphonate system. The materials structurally characterized in the study include the parent compound [Cu₂(H ₂O)₂(1,4-O₃PC₈H₈PO ₃)] (1); the o-phenanthroline derivatives: [Cu(H₂O)(o- Phen)(1,4-HO₃PC₈PO₃H)]·3H₂O (2·3H₂O), [Cu₂(H₂O)₂(1,4- O₃PC₈H₈PO₃)]·3H₂O (3·3H₂O), [Cu(o-phen)(1,4-HO₃PC₈H ₈PO₃H)]·3H₂O (4·3H₂O), [Cu(o-phen)(1,2-HO₃PC₈H₈PO₃H)] (5), and [Cu(o-phen)(1,3-HO₃PC₈H₈PO₃H)] (6); the 2,2′-bipyridine derivatives: [Cu₂(H₂O) ₂(bpy)₂(1,4-HO₃PC₈H ₈PO₃H₂)₂(HO₃PC ₈H₈PO₃H)]·H₂O (7·H₂O); [Cu(bpy)(1,4-HO₃PC₈H ₈PO₃H)]·2H₂O (8·2H₂O), and [Cu(bpy)(1,3-HO₃PC₈H₈PO₃H)] (9); the tetra-2-pyridylpyrazine materials: [Cu₂(H₂O) ₂(tpypyz)(1,4-HO₃PC₈H₈PO ₃H)₂·(1,4-H₂O₃PC ₈H₈PO₃H₂)₂·2H ₂O (10·(H₆₂O₃PC₈H ₈PO₃H₂)₂·2H₂O), [Cu₂(tpypyz)(1,2-HO₃PC₈H₈PO ₃H)₂]·2H₂O (11·2H₂O), and [Cu₄Cl₄(tpypyz)₂(1,4-H₂O ₃PC₈H₈PO₃H)₂]Cl ₂·H₂O₃PC₈H₈O ₃H₂·8H₂O (12·H₂O ₃PC₈H₈O₃H₂·8H ₂O); and the di-2,2′-pyridylamine compound [Cu(2,2dpy)(HO ₃PC₈H₈PO₃H)] (13). The role of the coligand in modifying the overall dimensionality of the ultimate products is apparent. Rather than observing the common pillared layer frameworks characteristic of metal-diphosphonate materials, the o-phenthroline derivatives, compounds 4 and 5 are two-dimensional, 3 and 6 are one-dimensional and 2 is molecular. For the 2,2′-bipyridyl analogues, 8 is two-dimensional while 9 is one-dimensional and 7 is molecular. Similarly, the tetra-2-pyridylpyrazine derivatives provide a one-dimensional material 10 and two molecular species 11 and 12.

Full text of DOI:10.1016/j.ica.2013.01.001

Inorganica Chimica Acta 403 (2013) 63–77
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Metal-organophosphonate chemistry: Hydrothermal syntheses and
structures of copper(II)-xylyldiphosphonates with organonitrogen
coligands
Tiffany M. Smith a, Jose Vargas b, Diona Symester a, Michael Tichenor a, Charles J. O’Connor b,
Jon Zubieta a,
⇑
a Department of Chemistry, Syracuse University, Syracuse, NY 13244, United States
b Advanced Materials Research Institute, College of Sciences, University of New Orleans, New Orleans, LA 70148, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 11 January 2013
The hydrothermal reactions of copper(II) acetate monohydrate or copper(II) chloride dihydrate with
xylyl-phosphonic acid derivatives in the presence of organonitrogen coligands yielded a series of com-
pounds of the Cu(II)/ligand/xylyl-diphosphonate system. The materials structurally characterized in
the study include the parent compound [Cu2(H2O)2(1,4-O3PC8H8PO3)] (1); the o-phenanthroline deriva-
tives: [Cu(H2O)(o-Phen)(1,4-HO3PC8PO3H)]ꢀ3H2O (2ꢀ3H2O), [Cu2(H2O)2(1,4-O3PC8H8PO3)]ꢀ3H2O (3ꢀ3H2O),
[Cu(o-phen)(1,4-HO3PC8H8PO3H)]ꢀ3H2O (4ꢀ3H2O), [Cu(o-phen)(1,2-HO3PC8H8PO3H)] (5), and [Cu
(o-phen)(1,3-HO3PC8H8PO3H)] (6); the 2,20-bipyridine derivatives: [Cu2(H2O)2(bpy)2(1,4-HO3PC8H8PO3
H2)2(HO3PC8H8PO3H)]ꢀH2O (7ꢀH2O); [Cu(bpy)(1,4-HO3PC8H8PO3H)]ꢀ2H2O (8ꢀ2H2O), and [Cu(bpy)(1,3-
HO3PC8H8PO3H)] (9); the tetra-2-pyridylpyrazine materials: [Cu2(H2O)2(tpypyz)(1,4-HO3PC8H8PO3H)2
ꢀ(1,4-H2O3PC8H8PO3H2)2ꢀ2H2O (10ꢀ(H62O3PC8H8PO3H2)2ꢀ2H2O), [Cu2(tpypyz)(1,2-HO3PC8H8PO3H)2]ꢀ2H2O
(11ꢀ2H2O), and [Cu4Cl4(tpypyz)2(1,4-H2O3PC8H8PO3H)2]Cl2ꢀH2O3PC8H8O3H2ꢀ8H2O (12ꢀH2O3PC8H8O3
H2ꢀ8H2O); and the di-2,20-pyridylamine compound [Cu(2,2dpy)(HO3PC8H8PO3H)] (13). The role of the
coligand in modifying the overall dimensionality of the ultimate products is apparent. Rather than
observing the common pillared layer frameworks characteristic of metal-diphosphonate materials, the
o-phenthroline derivatives, compounds 4 and 5 are two-dimensional, 3 and 6 are one-dimensional and
2 is molecular. For the 2,20-bipyridyl analogues, 8 is two-dimensional while 9 is one-dimensional and
7 is molecular. Similarly, the tetra-2-pyridylpyrazine derivatives provide a one-dimensional material
10 and two molecular species 11 and 12.
Coordination Polymers Special Issue
Keywords:
Coordination polymers of Cu(II)
Copper(II)-organodiphosphonate
compounds
Crystal structures
Magnetic properties of copper(II)
compounds
Copper(II)/organophosphonate/coligand
family
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
oxovanadium diphosphonates of the general class [V2O2(H2O)x
{O3P(CH2)nPO3}]ꢀxH2O exhibit three structure types depending on
Since the first reports of layered zirconium phenylphosphonate
in the 1970s [1,2], soon followed by the seminal work of Clearfield,
Bujoli, and Mallouk [3–9], metal phosphonate chemistry has
emerged in a vast literature detailing an unusual compositional
range and structural diversity [10,11]. The structural chemistry re-
veals three-dimensional open frameworks [12–14], pillared layer
materials [15–18], molecular phosphonate clusters and structures
incorporating organoimine templates or structure-directing units
[19–25].
A notable characteristic of the chemistry of metal-organ-
odiphosphonate materials is that both the length and chemical
identity of the organic tethering group can profoundly influence
the overall structure. In our own work, we have noted that the
the tether length n [26]. However, the structures of the oxovana-
dates of the aromatic diphosphonates are quite distinct from those
of their aliphatic counterparts [27]. Similar structural variations
have also been observed for the oxomolybdate-organodiphospho-
nate structures [28].
Copper diphosphonates are significant subclass of metal-organ-
odiphosphonate materials that have been designed with both ali-
phatic [29,30] and aromatic [31–34] linkers between the ligating
groups. While three dimensional ‘‘pillared layers’’ and other
three-dimensional frameworks are the rule for these materials,
the detailed connectivities within the Cu–P–O inorganic layers
may exhibit considerable variability. Furthermore, the structural
chemistry of copper-organodiphosphonates can be readily ex-
panded by introducing nitrogen-donor coligands [35–40] or by
exploiting the copper-diphosphonate moiety in the construction
of bimetallic oxide hybrid materials [41–46]. Encouraged by the of-
⇑
Corresponding author. Tel.: +1 315 443 2547; fax: +1 315 443 4070.
E-mail address: jazubiet@syr.edu (J. Zubieta).
0020-1693/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2013.01.001

64
T.M. Smith et al. / Inorganica Chimica Acta 403 (2013) 63–77
ten unique structural chemistry of the parent copper-aromatic-
diphosphonates, we recently reported on a study of the chemistry
of the Cu/ligand/(phenyl diphosphonate) system (where li-
gand = 2,2 bipyridine (bpy), o-phenanthroline (phen) and
2,20:6,200-terpyridine (terpy)) [47]. In an attempt to expand on
these results, we have undertaken an examination of structural
chemistry of the Cu(II)/ligand/xylyl-diphosphonate system in or-
der to assess the structural consequences of introducing the more
flexible xylyl-backbone in place of the rigid phenyl linker and of
diphosphonic acid (0.080 g, 0.30 mmol), and H2O (10 mL,
556 mmol) with the mole ratio of 1:0.52:0.71:1324 was stirred
briefly before heating to 120 °C for 48 h. The initial and final pH
values were 1 and 1, respectively. Blue blocks suitable for X-ray
diffraction were isolated in 30% yield. IR (KBr pellet, cmꢁ1):
3568(w), 3483(m), 3150(m), 3084(m), 2368(w), 2344(w),
1654(m), 1584(w), 1517(w), 1430(m), 1265(s), 1197(w), 1157(s),
1106(s), 1045(s), 940(s), 887(S), 852(m), 724(m), 550(s, 475(w).
Anal. Calc. for C40H52Cu2N4O20P4: C, 41.4; H, 4.48; N, 4.83. Found:
C, 41.5; H, 4.35; N, .68%.
2ꢁ
variations in the relative positions of the –CH2PO3 groups on
the ring. In this study, we present the structures of the parent com-
pound [Cu2(H2O)2(1,4-O3PC8H8PO3)] (1); the o-phenanthroline
2.4. Synthesis of Cu2(H2O)2(ophen)2(O3PC8H8PO3)ꢀ3H2O (3ꢀ3H2O)
derivatives:
[Cu(H2O)(o-phen)(1,4-HO3PC8H8PO3H)]ꢀ3H2O
(2ꢀ3H2O), [Cu2(H2O)2(1,4-O3PC8H8PO3)]ꢀ3H2O (3ꢀ3H2O), [Cu(o-
phen)(1,4-HO3PC8H8PO3H)]ꢀ3H2O (4ꢀ3H2O), [Cu(o-phen)(1,2-HO3
PC8H8PO3H)] (5), and [Cu(o-phen)(1,3-HO3PC8H8PO3H)] (6); the
2,20-dipyridine derivatives: [Cu2(H2O)2(bpy)2(1,4-HO3PC8H8PO3
H2)2(HO3PC8H8PO3H)]ꢀH2O (7ꢀH2O); [Cu(bpy)(1,4-HO3PC8H8PO3
H)]ꢀ2H2O (8ꢀ2H2O), and [Cu(bpy)(1,3-HO3PC8H8PO3H)] (9); the tet-
ra-2-pyridinylpyrazine materials: [Cu2(H2O)2(tpypyz)(1,4-HO3PC8
H8PO3H)2]ꢀ(1,4-H2O3PC8H8PO3H2)2ꢀ2H2O (10ꢀ(H2O3PC8H8PO3H2)2-
ꢀ2H2O), [Cu2(tpypyz)(1,2-HO3PC8H8PO3H)2]ꢀ2H2O (11ꢀ2H2O), and
[Cu4Cl4(tpypyz)2(1,4-H2O3PC8H8PO3H)2]Cl2ꢀH2O3PC8H8O3H2ꢀ8H2O
(12ꢀH2O3PC8H8O3H2ꢀ8H2O); and the di-2,20-pyridylamine com-
pound [Cu(2,2dpy) (HO3PC8H8PO3H)] (13).
A
solution of copper(II) chloride dihydrate (0.0714 g,
0.42 mmol), 1,10 phenanthroline (0.0392 g, 0.22 mmol), p-xylene-
diphosphonic acid (0.080 g, 0.30 mmol), H2O (10 mL, 556 mmol)
and 6 M NaOH (200 lL, 1.2 mmol) with the mole ratio of
1:0.52:0.71:1324:2.9 was stirred briefly before heating to 120 °C
for 48 h. The initial and final pH values were 6 and 5, respectively.
Blue rods suitable for X-ray diffraction were isolated in 5% yield. IR
(KBr pellet, cmꢁ1): 3496(m), 3366(m), 3253(m), 3078(m), 3055(m),
3008(m), 1642(m), 1625(m), 1580(w), 1510(m), 1427(s), 1152(s),
1150(s), 1097(s), 1046(s), 1010(s), 920(s), 858(s), 788(m),
737(w), 722(s), 570(s). Anal. Calc. for C16H20CuN2O7P: C, 43.0; H,
4.51; N, 6.27. Found: C, 42.6; H, 4.27; N, 6.33%.
2. Experimental
2.5. Synthesis of Cu(ophen)(HO3PC8H8PO3H)ꢀ3H2O (4ꢀ3H2O)
2.1. General procedures
A
solution of copper(II) chloride dihydrate (0.0714 g,
0.42 mmol), 1,10 phenanthroline (0.0392 g, 0.22 mmol), p-xylene-
diphosphonic acid (0.080 g, 0.30 mmol), and H2O (10 mL,
556 mmol) with the mole ratio of 1:0.52:0.71:1324 was stirred
briefly before heating to 150 °C for 48 h. The initial and final pH
values were 1 and 1, respectively. Blue blocks suitable for X-ray
diffraction were isolated in 50% yield. IR (KBr pellet, cmꢁ1):
3239(m), 3056(m), 1654(w), 1583(w), 1428(m), 1410(m),
1257(m), 1120(s), 1105(s), 1105(s), 1046(s), 950(s), 854(s),
724(s), 562(s). Anal. Calc. for C20H24CuN2O9P2: C, 42.7; H, 4.27; N,
4.98. Found: C, 42.6; H, 4.19; N, 5.11.
All chemicals were used as obtained without further purifica-
tion with the exception of p-xylene diphosphonic acid, ortho-xy-
lene diphosphonic acid and meta-xylene diphosphonic acid
which were synthesized in a similar fashion to the method pub-
lished in literature [30] using their respective dibromide starting
materials. Copper(II) acetate monohydrate (98%), copper(II) chlo-
ride dihydrate (97%), sodium orthovanadate (99.98%), 2,20-bipyri-
dine (99%), 1,10 phenanthroline (99%), tetra-2-pyridinylpyrazine
(97%), 2,20dipyridylamine (99%), sodium hydroxide (99.99%), and
hydrofluoric acid (48 wt.% in H2O) were all purchased from
Sigma–Aldrich. All syntheses were carried out in 23-mL poly(tetra-
fluoroethylene)-lined stainless steel containers under autogeneous
pressure. The pH of the solutions were measured prior to and after
heating using pHydrion vivid 1-11Ò pH paper. Water was distilled
above 3.0 MO in-house using a Barnstead Model 525 Biopure
Distilled Water Center.
2.6. Synthesis of [Cu(ophen)(HO3PC8H8PO3H)] (5)
A solution of copper(II) chloride dihydrate (0.0714 g, 0.42 mmol),
1,10 phenanthroline (0.0392 g, 0.22 mmol), o-xylene-diphosphonic
acid (0.080 g, 0.30 mmol), and H2O (5 mL, 278 mmol) with the
mole ratio of 1:0.52:0.71:662 was stirred briefly before heating
to 135 °C for 48 h. The initial and final pH values were 2 and 1,
respectively. Blue blocks suitable for X-ray diffraction were
~
2.2. Synthesis of Cu2(H2O)2(O3PC8H8PO3) (1)
isolated in 80% yield. IR (KBr pellet, cmꢁ1):
v = 3214(m),
A
solution of copper(II) chloride dihydrate (0.0714 g,
3054(m), 1702(w), 1583(m), 1422(s), 1134(w), 1107(s), 1065(s),
1027(s), 941(s), 872(s), 851(s), 788(s), 722(s), 587(s), 543(s),
521(s). Anal. Calc. for C20H18CuN2O6P2: C, 47.3; H, 3.54; N, 5.51.
Found: C, 47.0; H, 3.24; N, 5.40%.
0.42 mmol), 1,10 phenanthroline (0.0392 g, 0.22 mmol), p-xylene-
diphosphonic acid (0.080 g, 0.30 mmol), H2O (10 mL, 556 mmol)
and HF (500 lL, 14.5 mmol) with the mole ratio of
1:0.52:0.71:1324:34.5 was stirred briefly before heating to 100 °C
for 48 h. The initial and final pH values were 1 and 1, respectively.
Blue-green blocks suitable for X-ray diffraction were isolated in
20% yield. IR (KBr pellet, cmꢁ1): 3232(m), 3055(m), 1560(m),
1509(m), 1409(w), 1256(w), 1141(w), 1105(m), 1042(s), 984(s),
857(s), 510(s), 512(s). Anal. Calc. for C4H6CuO4P: C, 22.6; H, 2.82;
Found: C, 22.5; H, 2.93%.
2.7. Synthesis of [Cu(ophen)(HO3PC8H8PO3H)] (6)
A
solution of copper(II) chloride dihydrate (0.0714 g,
0.42 mmol), 1,10 phenanthroline (0.0392 g, 0.22 mmol), m-xy-
lene-diphosphonic acid (0.080 g, 0.30 mmol), and H2O (10 mL,
556 mmol) with the mole ratio of 1:0.52:0.71:1324 was stirred
briefly before heating to 120 °C for 72 h. The initial and final pH
values were 1 and 1, respectively. Green blocks suitable for X-ray
diffraction were isolated in 85% yield. IR (KBr pellet, cmꢁ1):
3429(w), 3064(w), 2909(w), 2366(w), 2344(w), 1605(w),
1584(w), 1519(w), 1488(w), 1429(m), 1296(w), 1225(m),
2.3. Synthesis of Cu(H2O)(ophen)(HO3PC8H8O3H)ꢀ3H2O (2ꢀ3H2O)
A
solution of copper(II) chloride dihydrate (0.0714 g,
0.42 mmol), 1,10 phenanthroline (0.0392 g, 0.22 mmol), p-xylene-

T.M. Smith et al. / Inorganica Chimica Acta 403 (2013) 63–77
65
1161(s), 1137(s), 1107(m). Anal. Calcd. C20H18CuN2O6P2: C, 47.3; H,
3.54; N, 5.51. Found C, 47.2; H, 3.46; N, 5.44%.
pound (12) 3422 (m), 3087(w), 2906(w), 2379(w), 2278(w),
1476(m), 1424(s), 12614(m), 1235(m), 1216(m), 1159(m),
1109(m), 1053(m), 1021(s), 1003(s), 936(s), 785(s), 563(s). Anal.
Calc. for C28H34CuN3O14P: C, 40.8; H, 4.13; N, 5.10. Found: C,
40.7; H, 4.06; N, 5.21%. Anal. Calc. for C40H40CuN6O14O4: C, 44.5;
H, 3.70; N, 7.78. Found: C, 43.9; H, 3.56; N, 7.66%.
2.8. Synthesis of Cu2(H2O)2(bpy)2(HO3PC8H8PO3H2)2
(HO3PC8H8PO3H)ꢀH2O (7ꢀH2O)
A
solution of copper(II) acetate monohydrate (0.0634 g,
0.32 mmol), 2,20bipyridine (0.034 g, 0.22 mmol), p-xylene-diphos-
2.12. Synthesis of [Cu2(tpypyz)(HO3PC8H8PO3H)2]ꢀ2H2O (11ꢀ2H2O)
phonic acid (0.080 g, 0.30 mmol), H2O (10 mL, 556 mmol) and HF
(500 lL, 14.5 mmol) with the mole ratio of 1:0.69:0.94:1738:45
A
solution of copper(II) acetate monohydrate (0.084 g,
was stirred briefly before heating to 120 °C for 72 h. The initial
and final pH values were 1 and 1, respectively. Blue blocks suitable
for X-ray diffraction were isolated in 90% yield. IR (KBr pellet,
cmꢁ1): 3409(s), 3092(m), 2902(m), 2344(w), 1663(w), 1607(s),
1569(w), 1473(w), 1446(m), 1300(s), 1104(s), 1097(m), 1059(m),
856(m), 768(m), 728(m), 562(s), 475(m). Anal. Calc. for C22H28-
CuN2O11P3: C, 40.5; H, 4.32; N, 4.29. Found: C, 40.4; H, 4.19; N,
4.16%.
0.421 mmol), tetra-2-pyridinylpyrazine (0.085 g, 0.22 mmol), o-
xylene-diphosphonic acid (0.080 g, 0.30 mmol), and H2O (10 mL,
556 mmol) with the mole ratio of 1:0.52:0.71:1321 was stirred
briefly before heating to 120 °C for 72 h. The initial and final pH
values were 4 and 4, respectively. Green rods suitable for X-ray dif-
fraction were isolated in 80% yield. IR (KBr pellet, cmꢁ1): 3435(m),
3077(w), 2914(w), 2892(w), 2367(w), 2344(w), 1601(m), 1477(m),
1419(m), 1304(w), 1259(m), 1165(m), 1113(s), 1067(s), 1022(m),
903(s), 786(s), 711(m), 576(m), 526(m), 483(m). Anal. Calc. for C72-
H82Cl6Cu4N12O26P6: C, 39.5; H, 4.04; N, 7.67. Found: C, 39.7; H,
3.86; N, 7.55%.
2.9. Synthesis of Cu(bpy)(HO3PC8H8PO3H)ꢀ2H2O (8ꢀ2H2O)
A
solution of copper(II) acetate monohydrate (0.0634 g,
0.32 mmol), sodium orthovanadate (0.058 g, 0.32 mmol), 2,20
2.13. Synthesis of Cu(2,20 dipyidylamine)(HO3PC8H8PO3H) (13)
bipyridine (0.034 g, 0.22 mmol), p-xylene-diphosphonic acid
(0.080 g, 0.30 mmol), H2O (10 mL, 556 mmol) and HF (500 lL,
A
solution
of
copper(II)
acetate
monohydrate
14.5 mmol) with the mole ratio of 1:1:0.69:0.94:1738:45 was stir-
red briefly before heating to 120 °C for 72 h. The initial and final pH
values were 1 and 1, respectively. Blue blocks suitable for X-ray
diffraction were isolated in 90% yield. IR (KBr pellet, cmꢁ1):
3447(w), 3150(m), 3090(w), 2902(w), 2361(s), 2342(s), 1602(s),
1560(w), 1510(w), 1444(s), 1251(s), 1203(s), 1056(s), 1010(s),
942(s), 857(m), 769(s), 729(m), 640(m), 563(s), 487(m). Anal. Calc.
for C18H22CuN2O8P2: C, 41.5; H, 4.23; N, 5.39. Found: C, 41.8; H,
4.44; N, 5.1%.
(0.094 g,0.47 mmol), 2,20 dipyridylamine (0.074 g,0.432 mmol),
m-xylene diphosphonic acid (0.152 g,0.57 mmol), (10 mL,
556 mmol) and HF (500 lL, 14.5 mmol) with the mole ratio of
1:0.92:1.2:1183:30.8 was stirred briefly before heating to 135 °C
for 48 h. The initial and final pH values were 1 and 1, respectively.
Green rods suitable for X-ray diffraction were isolated in 90% yield.
IR (KBr pellet, cmꢁ1): 3434(m), 2920(w), 2366(w), 2344(w),
1605(m), 1585(w), 1533(w), 1490(s), 1435(m), 1233(w), 1159(s),
1122(m), 1100(s), 948(m), 805(w), 765(m), 705(m), 530(w),
203(m), 465(w). Anal. Calc. for C36H38Cu2N6O12P4: C, 43.3; H,
3.84; N, 8.42. Found: C, 42.7; H, 3.76; N, 8.22%.
2.10. Synthesis of [Cu(bpy)(HO3PC8H8PO3H)] (9)
A
solution of copper(II) chloride dihydrate (0.0714 g,
0.42 mmol), 2,20 bipyridine (0.040 g, 0.26 mmol), m-xylene-
diphosphonic acid (0.080 g, 0.30 mmol), and H2O (10 mL,
556 mmol) with the mole ratio of 1:0.62:0.71:1324 was stirred
briefly before heating to 120 °C for 72 h. The initial and final pH
values were 1 and 1, respectively. Green plates suitable for X-ray
diffraction were isolated in 5% yield. IR (KBr pellet, cmꢁ1):
3448(s), 2951(m), 2919(m), 1475(w), 1458(w), 1226(m), 1120
(s), 1065(w), 1031(w), 939(m), 905(m), 779(m), 704(m), 518(m).
Anal. Calc. for C18H18CuN2O6P2: C, 44.6; H, 3.72; N, 5.39. Found:
C, 44.8; H, 3.44; N, 5.81%.
2.14. X-ray crystallography
Crystallographic data for all compounds were collected at low
temperature (90 K) on a Bruker Kappa APEX II diffractometer
equipped with an APEX II CCD system using Mo K
(k = 0.71073Å) [48,49]. The data were corrected for Lorentz and
polarization effects [50], and adsorption corrections were made
using SADABS [51]. The structures were solved by direct methods,
and refinements were made using the SHELXTL [52] crystallo-
graphic software. After first locating all of the nonhydrogen
atoms from the initial solution of each structure, the models
were refined against F2 using first isotropic and then anisotropic
a radiation
2.11. Synthesis of [Cu2(H2O)2(tpypyz)(HO3PC8H8PO3H)2]ꢀ(H2O3PC8H8
PO3H2)2ꢀ2H2O (10ꢀ(H2O3PC8H8PO3H2)2ꢀ2H2O) and [Cu4(Cl)4(tpypyz)2
(H2O3PC8H8PO3H)2] Cl2ꢀH2O3PC8H8O3H2ꢀ8H2O (12ꢀH2O3PC8H8O3
H2ꢀ8H2O)
thermal displacement parameters until the final value of
D/rmax
was less than 0.001. Hydrogen atoms were introduced in calcu-
lated positions and refined isotropically. Neutral atom scattering
coefficients and anomalous dispersion corrections were taken
from the International Tables, Vol. C. Crystallographic details for
the structures of 1–13 are summarized in Table 1. Selected bond
lengths and angles for the structures are given in Table 2. Images
of the crystal structures were generated using CrystalMakerÒ
[53].
A
solution of copper(II) chloride dihydrate (0.0714 g,
0.42 mmol), tetra-2-pyridinylpyrazine (0.085 g, 0.22 mmol), p-xy-
lene-diphosphonic acid (0.080 g, 0.30 mmol), and H2O (10 mL,
556 mmol) with the mole ratio of 1:0.52:0.71:1324 was stirred
briefly before heating to 120 °C for 72 h. After cooling to room tem-
perature, the solvent was allowed to evaporate to near dryness.
The initial and final pH values were 2 and 1, respectively. Light
green (10) and dark green (12) blocks suitable for X-ray diffraction
were isolated in 5% and 15% yield, respectively. IR (KBr pellet,
cmꢁ1): (10) 3725(m), 3428(m), 3100(m), 2344(m), 1655(w),
1599(w), 1509(m), 1478(m), 1428(m), 1310(w), 1099(s),
1070(m), 1019(m), 936(s), 801(m), 711(w), 574(m), 507(w). Com-
2.15. Thermogravimetric analyses
TGA data were collected on a TA instruments Q500 v6.7 Ther-
mogravimetric Analyzer. Data was collected on samples that ran-
ged between 5 and 10 mg , ramping the temperature at 10 °C/
°
min between ꢂ25–800 C.

66
T.M. Smith et al. / Inorganica Chimica Acta 403 (2013) 63–77
Table 1
Summary of crystal data for the compounds of this study.
[Cu2(H2O)2(O3PC8H8PO3)] (1)
[Cu(H2O)(o-phen)(HO3PC8H8PO3H)]ꢀ3H2O
(2ꢀ3H2O)
[Cu2(H2O)2(o-phen)2 (O3PC8H8PO3)]ꢀ6H2O
(3ꢀ6H2O)
Empirical
formula
Formula
weight
CuPO4C4H6
212.60
Cu2P4O20N4C40H52
CuPO7N2C16H20
1159.82
446.85
Crystal system monoclinic
triclinic
triclinic
ꢀ
ꢀ
Space group
P21/c
P1
P1
a (Å)
b (Å)
c (Å)
10.7962(19)
7.5630(13)
7.3761(12)
90.00
92.646(3)
90.00
601.63(18)
4
2.347
7.291(4)
11.546(6)
13.795(7)
99.645(9)
93.331(8)
98.882(8)
1126.9(11)
1
6.8782(12)
11.792(2)
11.808(2)
116.021(3)
93.494(3)
95.651(3)
850.6(3)
2
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (g cmꢁ3
)
1.709
1.173
1.745
1.423
l
(mmꢁ1
)
3.836
T (K)
90
90
90
Wavelength
0.71073
0.0233
0.0636
0.71073
0.0295
0.0806
0.71073
0.0534
0.1677
a
R1
b
wR2
[Cu(o-phen)(HO3PC8H8PO3H)]ꢀ3H2O (4ꢀ3H2O)
[Cu(o-phen)(HO3PC8H8PO3H)] (5)
CuP2O6N2C20H18
[Cu(o-phen)(HO3PC8H8PO3H)] (6)
CuP2O6N2C20H18
Empirical
formula
Formula
weight
CuP2O9N2C20H24
561.89
507.84
507.84
Crystal system triclinic
monoclinic
P21/n
triclinic
P1
ꢀ
ꢀ
Space group
P1
a (Å)
b (Å)
c (Å)
10.6221(8)
10.9369(9)
11.4714(9)
66.8400(10)
64.8830(10)
84.0880(10)
1106.13(15)
2
10.3496(18)
14.682(3)
12.523(2)
90.00
104.644(4)
90.00
1841.1(5)
4
1.832
9.7161(16)
11.3506(18)
11.3710(18)
116.331(2)
111.017(3)
92.971(3)
1015.3(3)
2
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (g cmꢁ3
)
1.687
1.189
1.661
1.276
l
(mmꢁ1
)
1.407
T (K)
90
90
90
Wavelength
0.71073
0.0279
0.0733
0.71073
0.0284
0.0663
0.71073
0.0200
0.0576
a
R1
b
wR2
[Cu2(H2O)2(bpy)2(HO3PC8H8PO3H2)2
(HO3PC8H8PO3H)]ꢀ2H2O (7ꢀ2H2O)
CuP3O11N2C22H28
[Cu(bpy)(HO3PC8H8PO3H)]ꢀ2H2O (8ꢀ2H2O) [Cu(bpy)(HO3PC8H8PO3H)] (9)
Empirical
formula
Formula
weight
CuP2O8N2C18H22
519.86
CuP2O6N2C18H18
483.82
652.91
Crystal system monoclinic
triclinic
P1
triclinic
P1
ꢀ
ꢀ
Space group
P21/n
a (Å)
b (Å)
c (Å)
9.8285(17)
16.843(3)
16.124(3)
90.00
106.353(2)
90.00
2561.1(8)
4
1.693
9.9436(13)
10.0660(14)
11.3028(15)
110.062(2)
108.237(2)
91.260(2)
998.6(2)
2
9.7629(14)
10.7730(16)
11.3060(17)
62.814(2)
89.181(3)
69.619(3)
976.5(2)
2
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (g cmꢁ3
)
1.729
1.306
1.646
1.322
l
(mmꢁ1
)
1.105
T (K)
90
90
90
Wavelength
0.71073
0.0280
0.0854
0.71073
0.0490
0.1108
0.71073
0.0267
0.0709
a
R1
b
wR2
[Cu2(H2O)2(tpypyz)(HO3PC8H8PO3H)2]ꢀ(H2O3PC8H8PO3H2)2ꢀ2H2O
(10ꢀ(H2O3PC8H8PO3H2)2ꢀ2H2O)
Empirical formula CuP4O14N3C28H34
[Cu2(tpypyz)(HO3PC8H8PO3H)2]ꢀ2H2O
(11ꢀ2H2O)
Cu2P4O14N6C40H40
1079.74
Formula weight
Crystal system
Space group
a (Å)
824.00
triclinic
triclinic
ꢀ
ꢀ
P1
P1
10.7313(16)
11.4004(16)
8.759(6)
9.008(6)
b (Å)

T.M. Smith et al. / Inorganica Chimica Acta 403 (2013) 63–77
67
c (Å)
(°)
b (°)
14.482(2)
78.920(2)
78.942(2)
75.774(2)
1665.8(4)
2
13.506(9)
89.597(11)
86.049(10)
71.486(9)
1008.0(12)
1
a
c
(°)
V (Å3)
Z
Dcalc (g cmꢁ3
)
1.643
0.922
1.779
1.295
l
(mmꢁ1
)
T (K)
90
90
Wavelength
0.71073
0.0294
0.0816
0.71073
0.0259
0.0757
a
R1
b
wR2
[Cu4Cl4(tpypyz)2(H2O3PC8H8PO3H)2]Cl2ꢀH2O3PC8H8PO3H2ꢀ8H2O (12ꢀH2O3PC8H8PO3H2ꢀ8H2O)
Empirical formula Cu4Cl6P6O26N12C72H82
[Cu(2,20dipyidylamine)(HO3PC8H8PO3H)] (13)
Cu2P4O12N6C36H38
997.68
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
2184.18
monoclinic
C2/c
14.0898(15)
20.701(3)
29.256(4)
90.00
triclinic
ꢀ
P1
9.722(4)
10.629(4)
10.723(4)
68.927(6)
67.969(6)
75.033(6)
948.6(6)
1
a
(°)
b (°)
92.153(2)
90.00
8526.9(17)
4
1.694
1.370
c
(°)
V (Å3)
Z
Dcalc (g cmꢁ3
)
1.746
1.365
l
(mmꢁ1
)
T (K)
90
90
Wavelength
0.71073
0.0551
0.1388
0.71073
0.0282
0.0790
a
R1
b
wR2
a
R1
wR2 = {
=
R
|Fo| ꢁ |Fc|/
R|Fo|.
P
2
2
R
[w(Fo2 ꢁ Fc2Þ ꢃ ½wðFo2Þ ꢃg1=2).
b
2.16. Magnetic susceptibility studies
more dimensions. The chain structures of compounds 3, 6 and 9
and the layers associated with compounds 4, 5 and 8 are character-
istic examples of the use of simple auxiliary chelates in the design
of lower dimensional materials.
Magnetic measurements were performed on a Quantum Design
SQUID, MPMS-XL magnetometer. Magnetic susceptibility mea-
surements for the complexes of this study were carried out in
the direct current (dc) mode in an applied field of 0.1 T in the 2–
300 K range. The measurements were performed on polycrystalline
samples of compound at 1000 Oe. Magnetic data obtained for sam-
ples were corrected for diamagnetic contributions by the use of the
Pascal constants.
However, such naïve design principles did not extend to the
chemistry of the Cu(II)/tpyprz/xylyl-diphosphonate system. Our
expectation was that the dipodal tpyprz would bridge copper sites
of copper-diphosphonate chains or networks to provide two- or
three-dimensional materials, or would decorate the surfaces of
chains or networks. Rather unexpectedly, only compound 10 exhib-
ited a chain structure while molecular species were observed for 11
and 12: a binuclear compound and a tetranuclear material, respec-
tively. In fact, the notable feature of the structural chemistry of the
copper(II)/xylyl-diphosphonate/organoimine chelate system is the
unusually high incidence of molecular species: in addition to 11
and 12, compounds 2, 7 and 13 are also molecular. This observation
also correlates with the tendency of the xylyl-diphosphonate li-
gands to adopt a variety of protonated forms, rather than the more
common fully deprotonated tetranegative anion {O3P-R-PO3}4ꢁ. As
noted previously [26], changes in the organic tether of the diphos-
phonate ligand result in profound structural consequences. In com-
paring the xylyl-diphosphonates and the phenyl-diphosphonates,
the behavior may reflect simply the different pK values of the par-
ent acids, as well as the geometric consequences of the increased
flexibility of the xylyl tether compared to the phenyl spacer.
The infrared spectra of compounds 1–13 exhibit a pattern of
two or three medium to strong bands in the 1000–1200 cmꢁ1
3. Results and discussion
3.1. Syntheses
Hydrothermal methods were first applied for the synthesis of
zeolites and metal phosphates [54,55]. More recently, the tech-
nique has been extended to the routine synthesis of metal oxides
and organic–inorganic composite materials [56–59]. Hydrothermal
syntheses are conventionally carried out in water at 120–250 °C at
autogenous pressure. Product composition depends on a number
of critical conditions, including pH of the medium, temperature
and hence pressure, the presence of structure-directing cations,
and the use of mineralizers. Since a variety of cationic and anionic
components may be present in solution, those of appropriate size,
geometry and charge to fulfill crystal packing requirements may be
selected from the mixture in the crystallization process. The tech-
nique thus exploits ‘‘self-assembly’’ of a solid phase from soluble
precursors at moderate temperatures.
Hydrothermal methods have been exploited for decades in the
preparation of metal-diphosphonate materials with pillared layer
structures, such as that of the parent compound [Cu2(H2O)2(1,4-O3-
PC8H8PO3)] (1). The introduction of auxiliary ligands, such as o-
phenanthroline and 2,20-bipyridyl, provides a method for reducing
the overall dimensionality of the phase by blocking coordination
sites at the metal and preventing structural expansion in one or
range attributed to m(P–O) of the phosphonate ligands. In addition,
compounds 2–4, 7–8, and 10–12 exhibit an intense broad band at
ca. 3100 cmꢁ1 assigned to
molecules.
m (O–H) of the coordinated water
3.2. Description of the X-ray structures of 1–13
The parent material, [Cu2(H2O)2(1,4-O3PCH2C6H4CH2PO3)] (1),
exhibits the prototypical pillared layer structure common to a host

68
T.M. Smith et al. / Inorganica Chimica Acta 403 (2013) 63–77
Table 2
Selected bond lengths (Å) and angles (°) for the compounds of this study.
[Cu2(H2O)2(O3PC8H8PO3)] (1)
Cu1 O3
Cu1 O4
Cu1 O2
Cu1 O1
Cu1 O4
P1 O2
1.917(2)
1.952(2)
1.975(2)
2.010(2)
2.351(2)
1.534(2)
1.536(2)
1.540(2)
O3 Cu1 O4
O2 Cu1 O1
O3 Cu1 O4
163.02(8)
170.55(8)
107.63(7)
P1 O3
P1 O4
[Cu(H2O)(o-phen)(HO3PC8H8PO3H)]ꢀ3H2O (2ꢀ3H2O)
Cu1 O4
Cu1 O2
Cu1 N1
Cu1 N2
Cu1 O1
P1 O4
P1 O2
P1 O3(H)
P2 O7
1.930(2)
1.935(2)
2.004(2)
2.014(2)
2.233(2)
1.507(2)
1.512(2)
1.571(2)
1.497(2)
1.502(2)
1.587(2)
O4 Cu1 N1
O2 Cu1 N2
170.80(7)
165.99(7)
P2 O5
P2 O6(H)
[Cu2(H2O)2(o-phen)2(O3PC8H8PO3)]ꢀ6H2O (3ꢀ6H2O)
Cu1 O1
Cu1 O3
Cu1 N2
Cu1 N1
Cu1 O2
P1 O4
1.924(2)
1.931(2)
2.026(2)
2.038(2)
2.265(2)
1.502(2)
1.528(2)
1.538(2)
O1 Cu1 N2
O3 Cu1 N1
O3 Cu1 O2
165.75(17)
166.90(17)
102.68(16)
P1 O1
P1 O3
[Cu(o-phen)(HO3PC8H8PO3H)]ꢀ3H2O (4ꢀ3H2O)
Cu1 O3
Cu1 O1
Cu1 N2
Cu1 N1
Cu1 O2
P1 O3
P1 O1
P1 O4(H)
P2 O2
1.943(2)
1.965(2)
2.011(2)
2.030(2)
2.220(2)
1.512(2)
1.513(2)
1.569(2)
1.507(2)
1.513(2)
1.582(2)
O3 Cu1 N2
O1 Cu1 N1
168.15(7)
163.02(7)
P2 O6
P2 O5(H)
[Cu(o-phen)(HO3PC8H8PO3H)] (5)
Cu1 O4
Cu1 O2
Cu1 N1
Cu1 N2
Cu1 O1
P1 O4
P1 O2
P1 O3(H)
P2 O1
1.943(2)
1.989(2)
2.045(2)
2.050(2)
2.154(2)
1.508(2)
1.529(2)
1.566(2)
1.502(2)
1.512(2)
1.599(2)
O4 Cu1 N1
O2 Cu1 N2
O2 Cu1 O1
N1 Cu1 O1
N2 Cu1 O1
157.54(8)
158.68(7)
100.29(7)
102.89(7)
100.57(7)
P2 O5
P2 O6(H)
[Cu(o-phen)(HO3PC8H8PO3H)](6)
Cu1 O2
Cu1 O1
Cu1 N2
Cu1 N1
Cu1 O3
P1 O2
P1 O3
P1 O4(H)
P2 O5
1.912(2)
1.948(2)
2.011(2)
2.028(2)
2.238(2)
1.513(2)
1.517(2)
1.570(2)
1.505(2)
1.511(2)
1.580(2)
O2 Cu1 N2
O1 Cu1 N1
O1 Cu1 O3
170.28(5)
148.31(5)
111.94(5)
P2 O1
P2 O6(H)
[Cu2(H2O)2(bpy)2(HO3PC8H8PO3H2)2
(HO3PC8H8PO3H)]ꢀ2H2O(7ꢀ2H2O)
Cu1 O3
Cu1 N1
Cu1 N2
Cu1 O1
P1 O2
1.969(2)
2.007(2)
2.015(2)
2.217(2)
1.494(2)
O3 Cu1 N1
167.02(6)

T.M. Smith et al. / Inorganica Chimica Acta 403 (2013) 63–77
69
P1 O6
P1 O7(H)
P2 O3
P2 O5
P2 O4
1.528(2)
1.562(2)
1.523(2)
1.533(2)
1.534(2)
1.480(2)
1.528(2)
1.717(2)
P3 O8
P3 O10*
P3 O9*
[Cu(bpy)(HO3PC8H8PO3H)]ꢀ2H2O (8ꢀ2H2O)
Cu1 O2
Cu1 O1
Cu1 N1
Cu1 N2
Cu1 O3
P1 O3
P1 O6
P1 O5
P2 O1
P2 O2
1.946(2)
1.965(2)
2.000(2)
2.006(2)
2.266(2)
1.517(2)
1.537(2)
1.545(2)
1.516(2)
1.516(2)
1.566(2)
O2 Cu1 N1
O1 Cu1 N2
N1 Cu1 O3
164.04(15)
166.11(15)
101.93(14)
P2 O4(H)
[Cu(bpy)(HO3PC8H8PO3H)] (9)
Cu1 O2
Cu1 O3
Cu1 N2
Cu1 N1
Cu1 O1
P1 O2
P1 O1
P1 O6(H)
P2 O4
1.916(2)
1.947(2)
2.003(2)
2.017(2)
2.294(2)
1.517(2)
1.522(2)
1.570(2)
1.506(2)
1.515(2)
1.580(2)
O2 Cu1 N2
O3 Cu1 N1
O3 Cu1 O1
171.78(5)
150.33(6)
111.67(5)
P2 O3
P2 O5(H)
[Cu2(H2O)2(tpypyz)(H2O3PC8H8PO3H)2 (HO3PC8H8PO3H)]
ꢀ(H2O3PC8H8PO3H2)2ꢀ2H2O (10ꢀ(H2O3PC8H8PO3H2)2ꢀ2H2O)
Cu1 O3
Cu1 O2
Cu1 N2
Cu1 N3
Cu1 N1
Cu1 O1
P1 O2
P1 O6
P1 O7(H)
P2 O9
2.588(2)
1.904(2)
1.957(2)
2.026(2)
2.049(2)
2.244(2)
1.518(2)
1.526(2)
1.563(2)
1.497(2)
1.543(2)
1.564(2)
1.514(2)
1.516(2)
1.573(2)
1.480(2)
1.555(2)
1.561(2)
O2 Cu1 N2
O2 Cu1 N1
N3 Cu1 N1
172.87(7)
101.70(7)
159.12(7)
P2 O8
P2 O10(H)
P3 O3
P3 O5
P3 O4(H)
P4 O11
P4 O12
P4 O13(H)
[Cu2(tpypyz)(HO3PC8H8PO3H)2]ꢀ2H2O (11ꢀ2H2O)
Cu1 O1
Cu1 N2
Cu1 N3
Cu1 N1
Cu1 O2
P1 O1
P1 O6
P1 O5
P2 O2
P2 O3
1.892(2)
1.971(2)
2.009(2)
2.024(2)
2.112(2)
1.508(2)
1.525(2)
1.528(2)
1.493(2)
1.533(2)
1.535(2)
O1 Cu1 N2
O1 Cu1 N1
N3 Cu1 N1
O1 Cu1 O2
164.12(6)
101.87(8)
152.67(7)
105.10(7)
P2 O4
[Cu4Cl4(tpypyz)2(H2O3PC8H8PO3H)2]Cl2ꢀH2O3PC8H8PO3H2ꢀ8H2O
(12ꢀH2O3PC8H8PO3H2ꢀ8H2O)
Cu1 N2
Cu1 N3
Cu1 N1
Cu1 Cl1
Cu1 O2
Cu2 N5
Cu2 N4
Cu2 N6
Cu2 Cl2
Cu2 O1
1.971(2)
2.021(2)
2.025(2)
2.216(2)
2.263(2)
1.948(2)
2.013(2)
2.021(2)
2.199(2)
2.324(2)
N3 Cu1 N1
N2 Cu1 Cl1
Cl1 Cu1 O2
N4 Cu2 N6
N5 Cu2 Cl2
N6 Cu2 Cl2
Cl2 Cu2 O1
157.78(16)
166.28(12)
103.59(9)
159.34(17)
164.85(13)
100.61(12)
106.35(9)
(continued on next page)

70
T.M. Smith et al. / Inorganica Chimica Acta 403 (2013) 63–77
P1 O2
P1 O3
P1 O1(H)
P2 O4*
P2 O6*
P2 O5
P3 O9
P3 O8
P3 O7(H)
1.522(2)
1.530(2)
1.563(2)
1.535(2)
1.522(2)
1.559(2)
1.503(2)
1.529(2)
1.568(2)
[Cu(2,20dipyidylamine)(HO3PC8H8PO3H)] (13)
Cu1 O2
Cu1 O1
Cu1 N3
Cu1 N1
P1 O2
P1 O1
P1 O3(H)
P2 O4
1.911(2)
1.922(2)
1.966(2)
1.977(2)
1.514(2)
1.518(2)
1.567(2)
1.490(2)
1.529(2)
1.582(2)
O1 Cu1 N3
O2 Cu1 N1
153.60(8)
150.28(8)
P2 O6
P2 O5(H)
*
Indicates disordered oxygen atom.
metal-diphosphonate phases and specifically to copper(II)-diphos-
phonate materials (Fig. 1a). The structure of the inorganic layer
{Cu2(H2O)2(O3P–)}n is similar to that previously observed for [Cu2
(H2O)2(1,4-O3PC6H4PO3)] [17]. The building block is a binuclear
unit of edge-sharing copper(II) square pyramids, linked to adjacent
binuclear units through bridging {O3P–} groups. The coordination
geometry at each copper site is defined by three phosphonate oxy-
gen donors and an aqua ligand in the basal plane, with a fourth
phosphonate oxygen occupying the apical position. Thus, each cop-
per square pyramid shares a corner with four phosphorus tetrahe-
dra and each phosphorus tetrahedron shares corners with four
copper square pyramids.
The connectivity pattern generates three distinct heterocyclic
units within the inorganic network. The first is the {Cu2O2} ring
associated with the edge-sharing interaction of copper square pyr-
amids. The remaining rings are the common {M2(2-O3PR)2} build-
ing units observed in many metal-organophosphonate structures.
One of these adopts the chain configuration of Fig. 1c or the DIV
Fig. 1. (a) A mixed polyhedral and ball-and-stick representation of the pillared-layer structure of [Cu2(H2O)2(1,4-O3PC8H8PO3)] (1); (b) a view of the structure of the inorganic
layer of 1. Color scheme: copper, blue polyhedra or spheres; phosphorus, yellow tetrahedra or spheres; oxygen, red spheres; carbon, black spheres. This scheme is used
throughout. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

T.M. Smith et al. / Inorganica Chimica Acta 403 (2013) 63–77
71
The structural influence of the o-phen ligand is apparent in this
instance. By occupying two coordination sites on the copper, the li-
gand prevents expansion into the pillared layered prototype for
metal-diphosphonate structures. However, the aqua ligand occu-
pying the apical coordination site is available for substitution
and, consequently, for structural expansion into two-dimensions
as illustrated by compound 4, shown in Fig. 4.
The network structure of 4 is constructed from the recurring
building units {Cu2(2-O,O0-phosphonate)2} linked through diphos-
phonate ligands into a layer structure. The structure may be de-
scribed as {Cu2(HO3PCH2C6H4CH2PO3H)2} chains, nearly identical
to those of compound 3 and running parallel to the crystallo-
graphic c-axis, connected through the diphosphonate ligands.
Thus, each binuclear subunit is linked to two adjacent subunits
in the chain and to two adjacent chains through the dipodal
ligands.
The o-phen coligands project above and below the layer and
serve to prevent structural expansion in the third dimension. The
chain substructure of 4 is clearly derived from that of 3 with dis-
placement of the aqua ligands by additional diphosphonate linkers
providing the expansion into two-dimensions. This observation
suggests that the chain of 3 may be a precursor to the formation
of the two-dimensional structure of 4 and consequently represents
a kinetic product.
Fig. 2. A view of the molecular structure of [Cu(H2O)(o-phen)(1,4-HO3PC8H8PO3H)]
(2). Color scheme: as above; nitrogen, light blue spheres. (For interpretation of the
references to color in this figure legend, the reader is referred to the web version of
this article.)
di–phosphato (O,O0) bridge mode of the scheme proposed by Bel-
tran-Porter et al. [60]. The second adopts a bowl-like configuration
due to edge-sharing to an adjacent copper site at one copper termi-
nus. This latter ring is akin to the DIII bridging mode of the Beltran-
Porter classification.
When o-phenanthroline is introduced as a coligand, the molec-
ular 1-D and 2-D structures of [Cu(H2O)(o-phen)(1,4-HO3PCH2C6
H4CH2PO3H)]ꢀ3H2O (2ꢀ3H2O), [Cu2(H2O)2(O3PCH2C6H4CH2PO3)]ꢀ
3H2O (3–3H2O) and [Cu(o-phen)(HO3PCH2C6H4CH2PO3H)]ꢀ3H2O
(4ꢀ3H2O), respectively, are observed.
It is noteworthy that either terminus of the diphosphonate li-
gand is protonated. The protonation sites are clearly established
by the P–O bond distances of 1.569(2) Å and 1.583(2) Å for the pro-
tonated P1–O4(H) and P2–O5(H) sites and of 1.512(3) Å for the
average of all others.
As shown in Fig. 2, the molecular structure of 2 consists of
binuclear copper(II) units. The copper geometry is ‘4+1’ axially
elongated square pyramidal, with the nitrogen donors of the
o-phen ligand and oxygen donors from two diphosphonate ligands
in the basal plane and an aqua ligand defining the apical position.
The structure exhibits the common {Cu2(2-O,O0phosphonate)2}
core. Only one terminus of each diphosphonate ligand is coordi-
nated, while the other is pedant and protonated. One oxygen site
at either terminus of the diphosphonate ligand is protonated, as
indicated by the P–O bond distances of 1.571(2) Å and
1.588(2) Å for P1–O3(H) and P2–O6(H), respectively, compared
to an average length of 1.505(3) Å for all other P–O bonds of
the structure.
The structural consequences of modifying the relative positions
of the {O3P-} units on the ring are illustrated by the structures of
[Cu(o-phen)(1,2-HO3PCH2C6H4CH2PO3H)]
(5)
and
[Cu(o-
phen)(1,3-HO3PCH2C6H4CH2PO3H)] (6). As shown in Fig. 5, the gen-
eral connectivity pattern for 5 is similar to that observed for 4.
Thus, the common {Cu2(2-O,O0-phosphonate)2} core connected
through doubly protonated {HO3PC8H8PO3H}2ꢁ ligands provides
the recurring structural motif. Once again each phosphonate ligand
bridges two adjacent binuclear cores and each binuclear unit is in
turn linked to four adjacent units. The major structural conse-
quence of shifting the relative positions of the {O3P–} groups from
1,4 in 4 to 1,2 in 5 is the relative packing of polyhedra within the
layer, as shown in Fig. 5c.
The one-dimensional structure of 3, shown in Fig. 3, is con-
structed from the common {Cu2(2-O,O0-phosphonate)2} units
linked through the organic tether of the diphosphonate ligand.
The copper sites once again display square pyramidal geometry
with the basal plane occupied by the o-phen nitrogen donors and
two phosphonate oxygen donors and a water molecule in the api-
cal position. The aqua ligands assume an anti-orientation with re-
spect to the {–Cu-O-P-O–}2 ring.
While the structure of 1,3-xylenediphosphonate derivative 6 is
one-dimensional, it is quite distinct from the 1-D structure of 3. As
shown in Fig. 6, the structure consists of the common {Cu2(2-O,O0-
phosphonate)2} secondary building units linked through the teth-
ers of dipodal ligands. In contrast to 3, the aqua ligand has been
displaced by an oxygen donor of a {1,3-HO3PC8H8PO3H}2ꢁ ligand.
As a result each binuclear copper subunit is linked to two adjacent
units of the chain through four diphosphonate linkers, rather than
Fig. 3. A ball-and-stick representation of the one-dimensional structure of [Cu2(H2O)2(1,4-O3PC8H8PO3)] (3).

72
T.M. Smith et al. / Inorganica Chimica Acta 403 (2013) 63–77
Fig. 4. (a) Ball-and-stick view of the layer structure of [Cu(o-phen)(1,4-HO3PC8H8PO3H)] (4) viewed approximately in the ac plane; (b) a polyhedral representation of the
structure viewed edge-onto the plane, parallel to the o-axis.
Fig. 6. A view of the one-dimensional structure of [Cu(o-phen)(1,3-HO3PC8H8PO3-
H)] (6).
two as in the structure of 3. The diphosphonate ligands again adopt
the {HO3PC8H8PO3H}2ꢁ protonation mode with O4 and O6 as the
clear protonation sites (P–OH distances of 1.570(1) Å and
1.580(1) Å compared to an average of 1.512(1) Å for all other P–O
distances).
Substitution of o-phenanthroline by 2,20-bipyridine provides
the molecular [Cu2(H2O)2(bpy)2(HO3PCH2C6H4CH2PO3H2)(HO3-
PCH2C6H4PO3H)]ꢀH2O (7ꢀH2O), the two-dimensional [Cu(bpy)(HO3-
PCH2C6H4CH2PO3H)]ꢀ2H2O (8ꢀ2H2O) and the one-dimensional
[Cu(bpy)(HO3PCH2C6H4CH2PO3H)] (9).
The molecular structure of 7 consists of an unusual binuclear
arrangement featuring copper(II) sites bridged through the {O3P–}
termini of a single diphosphonate ligand (Fig. 7). The copper sites
exhibit axially elongated square pyramidal geometry. The basal
Fig. 5. Polyhedral and ball-and-stick representation of the two-dimensional
structure of [Cu(o-phen)(1,2-HO3PC8H8PO3H)] (5) in the bc plane.

T.M. Smith et al. / Inorganica Chimica Acta 403 (2013) 63–77
73
plane is defined by the nitrogen donors of the bpy ligand and oxy-
gen donors from two diphosphonate ligands; an aqua ligand occu-
pies the apical position. One diphosphonate ligand bonds to a
single copper site through one oxygen donor, adopting the {HO3-
PC8H8PO3H2}1ꢁ protonation mode with one terminus pendant
and doubly protonated. The second diphosphonate ligand bridges
the two copper sites with oxygen atoms from either terminus.
The molecular structure of 7 may be contrasted with that of 2
which adopts the more conventional {Cu2(2-O,O0-phosphonate)2}
core structure.
On the other hand, the two-dimensional structure of 8, shown
in Fig. 8, is analogous to that of 4. The network consists of {Cu2
(bpy)2(HO3PC8H8PO3H)2} chains connected through the organic
tethers of ligands to adjacent chains, in a fashion identical to that
of 4.
The one-dimensional structure of 9 is analogous to that of 6,
with the o-phen ligand replaced by bpy (Fig. 9). The conservation
of certain structural motifs throughout the series of copper(II)/
diphosphonate/organonitrogen coligand series is not unexpected.
The introduction of the binucleating coligand tetrapyridinylpyr-
azine (tpyprz) unexpectedly results in a series of chain and
molecular species, [Cu2(H2O)2tpyprz)(1,4-HO3PCH2C6H4CH2PO3
H)2]ꢀ(H2O3PC8H8PO3H2)ꢀ2H2O (10ꢀH2O3PC8H8PO3H2ꢀ2H2O), [Cu2
(tpyprz)(1,2-HO3PCH2C6H4CH2PO3H)2]ꢀ2H2O (11ꢀ2H2O) and [CuCl4
(tpyprz)(1,4-H2O3PCH2C6H4CH2PO3H)2]Cl2ꢀH2O3PC8H8PO3H2ꢀ8H2O
(12ꢀH2O3PC8H8PO3H2ꢀ8H2O).
Fig. 7. A view of the molecular structure of [Cu2(H2O)2(bpy)2(1,4-HO3PC8H8PO3H2)2
(1,4-HO3PC8H8PO3H)] (7).
As shown in Fig. 10, the structure of 10 consists of {Cu2(H2O)2
(tpyprz)(1,4-HO3PCH2C2C6H4CH2PO3H)2}n chains and H2O and H2
O3PC8H8PO3H2 molecules. The copper sites of the chains exhibit
‘4+2’ axially distorted octahedral geometry with the pyridyl and
pyrazine nitrogen donors of one end of the tpyprz ligand and a
diphosphonate ligand in the equatorial plane and an aqua ligand
and a phosphonate oxygen occupying the axial positions. One
organophosphonate ligand coordinates to a copper site through a
single oxygen donor of one –PO3H terminus, leaving the second
terminus pendant. The second organophosphonate ligand bridges
copper centers from two adjacent {Cu2(tpyprz)}4+ binuclear units
through one oxygen donor of either terminus. Expansion into
one-dimension is thus achieved through this dipodal bridging
ligand.
As shown in Fig. 10b, each uncoordinated phosphonic acid, H2-
O3PC8H8PO3H2 engages in hydrogen bonding to four adjacent
chains to produce
framework.
a
hydrogen-bonded three-dimensional
The molecular structure of 11 exhibits two square pyramidal
copper(II) sites bridged by the tpyprz ligand (Fig. 11). The basal
planes of the square pyramidal copper centers again display three
nitrogen donors and a phosphonate oxygen in the basal plane. In
contrast to 10, the apical site is occupied by a second oxygen donor
from a chelating 1,2-xylyldiphosphonate ligand. The incorporation
of 1,2-xylyldiphosphonate derivative allows the chelate geometry
which would be precluded with the 1,3- and 1,4- forms for steric
and geometric reasons.
Fig. 8. A view of the two-dimensional structure of [Cu(bpy)(1,4-HO3PC8H8PO3H)]
(8).
Fig. 9. The one-dimensional structure of [Cu(bpy)(1,3-HO3PC8H8PO3H)] (9).

74
T.M. Smith et al. / Inorganica Chimica Acta 403 (2013) 63–77
Fig. 10. (a) A view of the one dimensional structure of [Cu2(H2O)2(tpyprz)(1,4-HO3PC8H8PO3H)2] (10) and the associated (1,4-H2O3PC8H8PO3H2) molecules of crystallization;
(b) a view down the a-axis of four adjacent [Cu2(H2O)2(tpyprz)(1,4-HO3PC8H8PO3H)2] chains and of the hydrogen bonding interactions with the interchain (1,4-
H2O3PC8H8PO3H2) molecule.
As illustrated in Fig. 12, the structure of 12 is tetranuclear and
incorporates a chloride donor at each copper site. The copper sites
are once again square pyramidal with three tpyprz nitrogen donors
and a chloride in the basal plane and an apical phosphonate oxy-
gen. The two {Cu2(tpyprz)Cl2}2+ units of the tetramer are linked
through two {H2O3PC8H8PO3H}1ꢁ phosphonates, each of which
connects copper sites from two binuclear units through oxygen do-
nors of the {HO3P–} terminus while the other terminus is pendant
and doubly protonated.
The introduction of 2,20-dipyridylamine as the coligand pro-
vided
a single material [Cu(dpa)(1,3-HO3PCH2C6H4CH2PO3H)]
(13), whose structure is shown in Fig. 13. The molecular structure
is similar to that of 2 with the exception that the apical aqua ligand
of 2 has been lost in 11. Consequently, the copper sites enjoy dis-
torted square planar geometry. The ligand imposed steric require-
ments are apparent in the more relaxed N–Cu–N angle in 11 of
92.4(1)° compared to a bite angle of 81.7(1)° in 2. The availability
of the apical site as well as the presence of the pendant {O3P–}
groups suggest that compounds such as 13, as well as 2, 7, 10
and 12 may serve as useful precursors for the syntheses of higher
dimensionality or bimetallic phases.
3.3. Thermal analyses
The thermal gravimetric analysis (TGA) plots of the compounds
of this study are quite complicated as there is a range of starting
Cu:P ratios, some of which do not match the stable phosphate
phases expected as the final decomposition products. Also, the
Fig. 11. A view of the binuclear structure of [Cu2(tpyprz)(1,2-HO3PC8H8PO3H)2]
(11).

T.M. Smith et al. / Inorganica Chimica Acta 403 (2013) 63–77
75
Fig. 14. The dependence of the magnetic susceptibility
v
(d) and effective
magnetic moment leff (s) of [Cu(o-phen)(1,4-HO3PC8H8PO3H)] (4) on temperature
T. The line drawn through the data is the fit to the Curie–Weiss law.
occurs in this range. The mechanism of dehydration is dependent
on topological and energetic considerations [64] such that it is ex-
pected that accessibility of water molecules to existing void spaces
in the crystal would result in low liberation temperatures as noted
for the waters of crystallization. On the other hand, the evacuation
of coordinated water requires higher temperature as these are con-
strained by the metal coordination sphere and do not have facile
access to the void spaces. The weight loss continuing beyond
800 °C is attributed to the pyrolysis of the o-phen ligand and the
production of the final products, most likely a mixture of Cu2P2O7
and CuO.
Fig. 12. The structure of the molecular, tetranuclear [Cu4Cl4(tpyprz)2(1,4-H2O3PC8-
H8PO3H)2]2ꢁ anion. Color scheme: as above with chlorine as light green spheres.
Similar profiles are observed for compounds 3, 4, 7, 8, 10, 11 and
12 which contain water molecules of crystallization. The profiles
for compounds 5, 6, 9 and 13 are similar in the region above
250 °C but show no weight loss below that temperature since there
is no water of crystallization associated with these compounds.
decomposition processes do not appear to be complete even at
800 °C, as evidenced by a gradual loss continuing at the limiting
temperature of our instrument. All TGA profiles can be found in
the ESI..
The TGA of compound 1 shows an initial weight loss of ca.
8.0% corresponding to the loss of the weakly coordinated water
ligands (8.5%, theoretical). This initial weight loss is followed
by a series of overlapping weight losses starting at 250 °C and
continuing to 800 °C. Over this range there are three processes
occurring: the condensation of the hydrogen phosphonate
groups, the pyrolysis of the organic group, and the oxidation
and loss of P2O5 [63]. This decomposition pattern likely results
in a mixture of final products. Powder XRD analysis of the pyro-
lysis product shows that it contains Cu2P2O7. However, the ob-
served loss of ca. 34.5% suggests further decomposition to a
mixture of Cu2P2O7 and CuO.
The TGA of compound 2 exhibits a generally similar pattern
with an initial weight loss between room temperature and
125 °C attributed to the loss of water of crystallization. This dehy-
dration process is followed by a plateau of stability between 125 °C
and 250 °C. Subsequently, a pattern of overlapping weight losses
between 250 °C and 500 °C may correspond to the condensation
of the hydrogen phosphonate groups, the pyrolysis of the phospho-
nate organic group, and the oxidation and loss of P2O5, as observed
for compound 1. The loss of the coordinated water molecules also
3.4. Magnetism
Magnetic susceptibility measurements of complexes 1, 2, 4–8,
and 11–13 were performed on polycrystalline samples of com-
pound at 1000 Oe over the temperature range 2–300 K (Supple-
mentary Figs. S40-–S49). Compounds 3, 9 and 10 could not be
separated from paramagnetic impurities and consequently were
not studied. The magnetic data for compounds 1, 2, 5–8, 11 and
13 conformed to simple Curie–Weiss behavior. A temperature-
independent paramagnetism term (TIP) was added to take into ac-
count the baseline correction. The final expression used to fit the
susceptibility data was the following:
Ng2
3kB½T ꢁ hꢃ
l
2BSðS þ 1Þ
v
¼
vh þ TIP ¼
þ TIP
ð1Þ
As a function of the effective magnetic moment:
l2eff
8½T ꢁ hꢃ
v
¼
vh þ TIP ¼
þ TIP
ð2Þ
where
l2eff ¼ g2SðS þ 1Þ:
Compound 6 gives characteristic best fit values for l2eff , h and g
of 1.90 0.25, ꢁ0.27 0.09 and 2.12, respectively, which are con-
sistent with d9-Cu(II) sites (S = 1/2).
In contrast, compounds 2, 4 and 12 exhibit
v vs. T plots indic-
ative of low temperature magnetic ordering (Fig. 14). The plots
for compounds 4 and 12 exhibit distinct maxima below 50 K
and h values of ꢁ13.4 and ꢁ36.7, respectively, suggesting antifer-
romagnetic coupling between the copper(II) sites. The magnetic
behaviors of these latter compounds exhibit significant field
dependences. The contrasting behavior of the magnetic properties
Fig. 13. The molecular structure of [Cu(2,2-dpy)(HO3PC8H8PO3H)] (13).

76
T.M. Smith et al. / Inorganica Chimica Acta 403 (2013) 63–77
Table 3
Selected structural features for the copper-phosphonates of this study and of representative copper-phosphonates.
Compound
Dimensionality Cu coordination
Phosphonate coordination
Reference
(a) Aromatic di- and triphosphonate
[Cu2(H2O)2(O3PC8H8PO3)] (1)
3-D
{CuO5} square
planar
{CuN2O3} square
planar
{CuN2O3} square
planar
{CuN2O3} square
planar
One terminus bridges 3 Cu
sites
One terminus bridges two
Cu sites, one is pendant
Each terminus bridges two
Cu sites
One terminus bridges two
Cu sites, one bridges one Cu
site
This work
This work
This work
This work
[Cu(H2O)(o-phen)(HO3PC8H8PO3H)]ꢀ3H2O (2ꢀ3H2O)
[Cu2(H2O)2(o-phen)2(O3PC8H8PO3)]ꢀ6H2O (3ꢀ6H2O)
[Cu(o-phen)(HO3PC8H8PO3H)]ꢀ3H2O (4ꢀ3H2O)
Molecular
1-D
2-D
[Cu(o-phen)(HO3PC8H8PO3H)] (5)
[Cu(o-phen)(HO3PC8H8PO3H)] (6)
2-D
1-D
{CuN2O3} square
planar
One terminus bridges two
Cu sites, one bonds to one
Cu site
One terminus bridges two
Cu sties, one bonds to one
Cu site
This work
This work
{CuN2O3} square
planar
[Cu2(H2O)2(bpy)2(HO3PC8H8PO3H2)2(HO3PC8H8PO3H)]ꢀ2H2O(7ꢀ2H2O)
[Cu(bpy)(HO3PC8H8PO3H)]ꢀ2H2O (8ꢀ2H2O)
Molecular
2-D
{CuN2O3} square
planar
{CuN2O3} square
planar
One terminus bridges to
one Cu site, one is pendant
One terminus bridges two
Cu sites, one bonds to one
Cu site
This work
This work
[Cu(bpy)(HO3PC8H8PO3H)] (9)
1-D
1-D
{CuN2O3} square
planar
One terminus bridges two
Cu sites, one bonds to one
Cu site
This work
This work
[Cu2(H2O)2(tpypyz)(H2O3PC8H8PO3H)2(HO3PC8H8PO3H)]ꢀ(H2O3PC8H8PO3H2)2ꢀ2H2O
(10ꢀ(H2O3PC8H8PO3H2)2ꢀ2H2O)
{CuN2O4} distorted One terminus bridges two
octahedron
Cu sites, one terminus is
pendant, one is
uncoordinated
[Cu2(tpypyz)(HO3PC8H8PO3H)2]ꢀ2H2O (11ꢀ2H2O)
Molecular
Molecular
Molecular
Molecular
Molecular
1-D
{CuN2O3} square
planar
{CuN3OCl} square
planar
One terminus bridges one
Cu site, one is pendant
One terminus bridges two
Cu sites, one is pendant
One terminus bridges two
Cu sites, one is pendant
Each terminus bonds to a
single Cu site
Each terminus bonds to a
single Cu site
Each terminus bonds to a
single Cu site
This work
This work
This work
[47]
[Cu4(Cl)4(tpypyz)2(H2O3PC8H8PO3H)2]Cl2ꢀH2O3PC8H8PO3H2ꢀ8H2O
(12ꢀH2O3PC8H8PO3H2ꢀ8H2O)
[Cu(2,20dipyidylamine)(HO3PC8H8PO3H)] (13)
{CuN2O2}
tetrahedral
{CuO2N2} square
planar
{CuON2} Cu(I), ‘‘T’’
shaped
{CuO3N2} ‘4+1’
type
{CuO4N2} distorted Each terminus bonds to a
octahedron single Cu Site
{CuO4N2} distorted Each terminus bonds to a
[Cu(ophen){HO3P(C12H8)PO3H}]
[{Cu(ophen)}2{HO3P(C12H8)PO3H}]
[Cu(terpy){HO3P(C12H8PO3H}]ꢀH2O
Cu(HO3PCH2)2C6H4[N(CH)4CC(CH)4N]ꢀ2H2O
Cu(HO3PCH2)2C6H4[N(CH)4CC(CH)4N]ꢀ2H2O
[47]
[47]
2-D
[61]
2-D
[61]
octahedron
single Cu Site
(b) Aliphatic diphosphonates with secondary nitrogen-donor ligands
[Cu3(HL)2(Hpyterpy)2]ꢀ2H2O HL5 = 1-hydroxyethylidenediphosphonic acid
3-D
{CuO3N} distorted
tetrahedral and
{CuO4N} square
planar
Two termini bridge 3 Cu
sites and two termini
bridge two Cu sites
[62]
[Cu4(HL)2(4,40-bipy)(H2O)5] HL5 = 1-hydroxyethylidenediphosphonic acid
[Cu(bpy){HO3P(CH2)3PO3H}]
2-D
2D
{CuNO4} and
{CuO5} square
planar
{CuO3N} square
pyramids
One terminus bridges 3 Cu
sites, one terminus bridges
two Cu sites
One terminus bridges 2 Cu
sites; the second bonds to a
single site
Each terminus bonds to a
single Cu site
Each terminus chelate a Cu [37]
site
[62]
[36]
[36]
[Cu(4,40-bpy)(H2O)2{HO3P(CH2)4PO3H}]
[{Cu(phen)(H2O)}2(O3PCH2CH2PO3)]
[Cu(terpy)(HO3PCH2CH2PO3H)]
2D
[CuO4N2} ‘4+2’
octahedra
{Cu(O3N2} square
pyramids
{CuO2N3} square
pyramids
Molecular
1-D
Each terminus bonds to a
single Cu site
[37]
[Cu(mephenterpy){HO3P(CH2)4PO3H}]
1-D
{CuO2N3} square
pyramids
Each terminus bonds to a
single Cu site
[39]
of compounds 2, 4 and 12 and the other compounds of this study
presumably reflects the different overlaps and orientations of the
magnetic orbitals. However, since the fitting of the magnetic data
for compounds 2, 4 and 12 requires further investigation, the
interpretation of the trends in the magnetism of these com-
pounds remains speculative. These preliminary magnetic investi-
gations will be expanded upon in future communications in light
of field dependent studies.
4. Conclusions
Hydrothermal synthesis has been used to prepare thirteen new
copper-organodiphosphonate compounds. The parent compound
[Cu2(H2O)2(1,4-O3PC8H8PO3)] (1) exhibits the common pillared
layer structure. The remaining compounds incorporate organoi-
mine chelates to occupy coordination sites on the copper centers
in order to reduce the dimensionality of the resultant copper(II)/

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Of the o-phenthroline derivatives, compounds 4 and 5 are two-
dimensional, 3 and 6 are one-dimensional and 2 is molecular. For
the 2,20-bipyridyl analogues, 8 is two-dimensional while 9 is one-
dimensional and 7 is molecular. Most curiously, the tetra-2-pyr-
idylpyrazine derivatives provide a one-dimensional material 10
and two molecular species 11 and 12. In view of the bridging coor-
dination generally adopted by tpyprz, we had naively assumed that
copper-diphosphonate chains linked through tpyprz rods into 2-D
or even 3-D structures would predominate.
The unpredictability of the structures reflects a number of
structural determinants. The coordination geometry of the copper
is variable with ‘4+1’ and ‘4+2’ axially distorted geometries and
even square planar geometry making regular appearances. Vari-
able aqua coordination is also common. The organophosphonate li-
gands can coordinate in a variety of ways and can display different
degrees of protonation. Pendant –PO3 termini are not uncommon
and a given –PO3 terminus can bond to one to four metal sites. Fi-
nally the identity of the tether of the diphosphonate ligand can also
serve as a structural determinant; that is, it does not function so-
lely as an innocent spacer.
Acknowledgement
This work was funded by a grant from the National Science
Foundation (CHE-0907787).
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Appendix A. Supplementary material
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CCDC 881705–881717, comprises the final atomic coordinates
for all atoms, thermal parameters, and a complete listing of bond
distances and angles, contain the supplementary crystallographic
data for this paper. 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 associ-
ated with this article can be found, in the online version, at http://
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