Angewandte
Communications
Chemie
Table 1: Crystal data and refinement results of new homochiral compounds synthesized herein.[11]
Code
Formula
Space group a [ꢀ]
b [ꢀ]
c [ꢀ]
b
R(F)
Flack
Net
RR-H2cam
SS-H2cam
CPM-311-RR
CPM-312-SR(Mg) Mg3(HCOO)4(SR-cam)
CPM-312-RR(Mg) Mg3(HCOO)4(RR-cam)
CPM-312-SS(Mg) Mg3(HCOO)4(SS-cam)
l-C10H16O4
d-C10H16O4
(Me4N)In(RR-cam)2
P41212
P43212
P6122
P31
P32
P31
P32
P32
P6122
P3221
P21
13.8060(16) 13.8060(16) 22.455(3)
90
90
90
90
90
90
90
0.0376 0.0(8)
0-D
0-D
13.820(3)
12.361(9)
13.820(3)
12.361(9)
22.486(4)
37.86(3)
0.0531 À0.2(9)
0.0431 0.026(14) qtz
14.7922(12) 14.7922(12) 7.3144(14)
14.8000(2) 14.8000(2) 7.4722(2)
14.8963(14) 14.8963(14) 7.4374(7)
0.0582 0.0(3)
0.0531 0.0(2)
0.0468 0.11(13)
0.0520 0.09(3)
0.0389 0.008(10) eta
0.0783 0.040(14) uon
0.0945 0.064(13) qtz
eta
eta
eta
eta
CPM-312-RS(Co)
CPM-312-RR(Co) Co3(HCOO)4(RR-cam)
Co3(HCOO)4(RS-cam)
14.8259(7)
14.7363(2)
19.2517(8)
14.8259(7)
14.7363(2)
19.2517(8)
7.4062(4)
7.55860(10) 90
33.0352(16) 90
CPM-313-RR
CPM-314-RR
CPM-315-RR
CPM-316-RR
CPM-317-RR
Cu2(RR-cam)2(DMF)2
Cu2(RR-cam)2(DMEU)2
Cu2(RR-cam)2(NMF)2.5
Cu2(RR-cam)2(DEA)2
Co2(OH)(RR-cam)-
12.2369(15) 12.2369(15) 39.188(6)
10.698(3) 26.971(8) 11.225(3)
10.9533(16) 13.3126(19) 13.0115(19) 108.932(4) 0.0863 0.12(2)
90
107.247(6) 0.0458 0.057(12) dia
P21
P21
sql
ecu
13.525(5)
12.735(4)
14.421(5)
112.957(7) 0.0710 0.00(2)
(HRR-cam)(H2RR-cam)2
Cu2(RR-cam)2(bpy)
CPM-332-RR
P21
13.317(4)
12.797(4)
13.946(4)
90.965(7) 0.0841 0.07(3)
pcu
cam and can lead to materials with greater porosity. One
striking feature of RR-cam is its powerful ability to form 4-
connected intrinsically chiral 3D framework.
understood as internal pore-surface modification with differ-
ent chiral ligands on the same primary framework. CPM-312
adopts the chiral eta net with Mg-HCOO helices (31 or 32).
Interestingly, there is a relationship between the helix and the
auxiliary ligands. When the auxiliary ligand is RS-cam or RR-
cam, the inorganic chains adopt 32 helix. However, when the
auxiliary ligand is SR-cam or SS-cam, the chains adopt 31
helix. This shows that the absolute helicity of chain is
controlled by the stereochemistry around C1 of camphorates.
CPM-313-RR to CPM-316-RR, based on copper paddle-
wheel dimers, illustrate that diastereoisomerization of the
chiral linker (transition from cis RS-cam to trans RR-cam)
results in greater structural diversity (Figure 3). Moreover,
these materials demonstrate the powerful ability of RR-cam
to construct various 4-connected frameworks, even from
square-planar nodes. By flipping one chiral center on the
cyclopentane ring, RR-cam gives dramatically different con-
figurations from RS-cam. Such a difference is further
amplified when coordinated to metal nodes. As a result, the
relative orientation between adjacent metal nodes is affected,
leading to various framework types. It is worth noting that
copper paddlewheel is a planar 4-connected node and has
difficulty forming 3D frameworks with dicarboxylate, in the
absence of auxiliary ligands such as 4,4’-bipyridine. RS-cam
itself tends to form a square net with copper dimers. In
contrast, by using its diastereoisomer RR-cam, we have made
several copper-dimer-based phases in different topologies. A
prominent example is CPM-313-RR which exhibits a very
rare intrinsically chiral 4-connected net (uon). Adding to the
structural diversity, the formation of these 4-connected nets
are sensitive to the solvent used. Four structure types have
been obtained in DMF (CPM-313, uon), DMEU (CPM-314,
qtz), NMF (CPM-315, dia), and DEA (CPM-316, sql),
respectively. In comparison, the assembly between RS-cam
and copper dimer is not much sensitive to the reaction
conditions. This show that RR-cam can serve as a platform for
exploring the synthetic and structural chemistry of homo-
chiral structures. The versatility of RR-cam was observed
again in CPM-317-RR, a cobalt compound. CPM-317-RR
features V-shaped cobalt dimers (Supporting Information,
Figure S6) connected by eight RR-cam to form the ecu net.
CPM-311 and CPM-312 families of materials, in all four
RS-, SR-, RR-, and SS-homochiral forms, demonstrate an
unprecedented solid-state phenomenon: enantiomeric, dia-
stereomeric, and isoreticular MOFs. There are many exam-
ples of isoreticular MOFs, however, they are rarely diaste-
reomeric at molecular level. It is thus a truly intriguing solid-
state phenomenon when diastereomers can form isoreticular
MOFs with nearly identical crystal structures. It means that it
is now possible to switch the chiral environment by replacing
an enantiopure ligand with its chiral diastereomer without
altering its crystal structure and framework topology. In this
work, we were able to accomplish this type of chirality
switching when the chiral ligand is either a crosslinking ligand
or a pendant ligand.
CPM-311-RR, formulated as (Me4N)In(RR-cam)2 with
RR-cam as crosslinker, features uninodal 4-connected quartz
(qtz) net with four RR-cam ligands chelating to the indium
monomer (Figure 2a). The structure integrates three types of
chirality features: the 0-D chirality of RR-cam, the intrinsic
3D chiral qtz net, and 1D absolute helicity. CPM-311-RR and
its diastereomeric CPM-311-RS have the same structure, with
the only difference being the chirality around one of the two
chiral centers (C3; Figure 2a). Mimicking the stereoisomer
concept in molecules, herein we name these isoreticular
MOFs as stereoiso-MOFs, including diastereo-MOFs and
enantio-MOFs.
CPM-312 is an excellent example that illustrates the close
correlation between an individual chiral center and the
overall absolute helicity. Specifically, a change in the chirality
of C3 does not change the absolute helicity, while a change in
the chirality of C1 switches the absolute helicity of Mg2+-
format helix to which chiral camphorates are attached. CPM-
312 has honeycomb channels with a Mg2+-format backbone.
RR-cam acts as an auxiliary ligand attached on the wall of the
hexagonal channel (Figure 2b). Together with CPM-312-SS,
CPM-312-RS, and CPM-312-SR, they form another family of
stereoisomeric MOFs with the same structure, but different
chiral properties. These four CPM-312 compounds can be
2
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2018, 57, 1 – 6
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