70 research outputs found
Alignment of Acentric Units in Infinite Chains: A “Lock and Key” Model
Polar
chains built from acentric building units are of importance to investigate
the mechanisms driving the polar alignment in the solid state. Our
attempts to engineer polar chains in mixed metal oxide fluorides M′(2,2′-bpy)(H<sub>2</sub>O)<sub>2</sub>MO<sub><i>x</i></sub>F<sub>6–<i>x</i></sub> compounds [M′/M = Cu/Ti, Cu/V, Cu/Nb, Cu/Mo,
Zn/Mo, and Zn/W] were successful using a combination of acentric anions
[MO<sub><i>x</i></sub>F<sub>6–<i>x</i></sub>]<sup>2–</sup> and acentric cations [M′(2,2′-bpy)(H<sub>2</sub>O)<sub>2</sub>]<sup>2+</sup>. A new general insight is also
revealed: the alignment of polar units can be described with a “lock
and key” model. The role of both the key (the acentric unit)
and the lock (its environment) on the polarity in infinite chains
is discussed
Preservation of Chirality and Polarity between Chiral and Polar Building Units in the Solid State
The new lamellar phases [Zn(2,2′-bpy)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>](ZrF<sub>6</sub>)·3H<sub>2</sub>O (<b>I</b>) and [Ni(2,2′-bpy)<sub>3</sub>](MoO<sub>2</sub>F<sub>4</sub>)·5H<sub>2</sub>O (<b>II</b>) (bpy
= bipyridine),
which are built from a chiral cation and respectively an inherently
nonpolar and a polar anion, provide two contrasting structures with
respect to chirality and polarity in the solid state. Each nonpolar
layer of <b>I</b> contains enantiomers of both handednesses;
conversely, each layer of <b>II</b> contains only a Δ
or Λ enantiomer and polar anions oriented along the <i>b</i> or −<i>b</i> axes. A comparison with
previously reported structures reveals which combinations and interactions
between chiral and polar basic building units can preserve elements
of polarity and chirality in the solid state
Alignment of Acentric Units in Infinite Chains: A “Lock and Key” Model
Polar
chains built from acentric building units are of importance to investigate
the mechanisms driving the polar alignment in the solid state. Our
attempts to engineer polar chains in mixed metal oxide fluorides M′(2,2′-bpy)(H<sub>2</sub>O)<sub>2</sub>MO<sub><i>x</i></sub>F<sub>6–<i>x</i></sub> compounds [M′/M = Cu/Ti, Cu/V, Cu/Nb, Cu/Mo,
Zn/Mo, and Zn/W] were successful using a combination of acentric anions
[MO<sub><i>x</i></sub>F<sub>6–<i>x</i></sub>]<sup>2–</sup> and acentric cations [M′(2,2′-bpy)(H<sub>2</sub>O)<sub>2</sub>]<sup>2+</sup>. A new general insight is also
revealed: the alignment of polar units can be described with a “lock
and key” model. The role of both the key (the acentric unit)
and the lock (its environment) on the polarity in infinite chains
is discussed
Alignment of Acentric Units in Infinite Chains: A “Lock and Key” Model
Polar
chains built from acentric building units are of importance to investigate
the mechanisms driving the polar alignment in the solid state. Our
attempts to engineer polar chains in mixed metal oxide fluorides M′(2,2′-bpy)(H<sub>2</sub>O)<sub>2</sub>MO<sub><i>x</i></sub>F<sub>6–<i>x</i></sub> compounds [M′/M = Cu/Ti, Cu/V, Cu/Nb, Cu/Mo,
Zn/Mo, and Zn/W] were successful using a combination of acentric anions
[MO<sub><i>x</i></sub>F<sub>6–<i>x</i></sub>]<sup>2–</sup> and acentric cations [M′(2,2′-bpy)(H<sub>2</sub>O)<sub>2</sub>]<sup>2+</sup>. A new general insight is also
revealed: the alignment of polar units can be described with a “lock
and key” model. The role of both the key (the acentric unit)
and the lock (its environment) on the polarity in infinite chains
is discussed
Preservation of Chirality and Polarity between Chiral and Polar Building Units in the Solid State
The new lamellar phases [Zn(2,2′-bpy)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>](ZrF<sub>6</sub>)·3H<sub>2</sub>O (<b>I</b>) and [Ni(2,2′-bpy)<sub>3</sub>](MoO<sub>2</sub>F<sub>4</sub>)·5H<sub>2</sub>O (<b>II</b>) (bpy
= bipyridine),
which are built from a chiral cation and respectively an inherently
nonpolar and a polar anion, provide two contrasting structures with
respect to chirality and polarity in the solid state. Each nonpolar
layer of <b>I</b> contains enantiomers of both handednesses;
conversely, each layer of <b>II</b> contains only a Δ
or Λ enantiomer and polar anions oriented along the <i>b</i> or −<i>b</i> axes. A comparison with
previously reported structures reveals which combinations and interactions
between chiral and polar basic building units can preserve elements
of polarity and chirality in the solid state
Alignment of Acentric Units in Infinite Chains: A “Lock and Key” Model
Polar
chains built from acentric building units are of importance to investigate
the mechanisms driving the polar alignment in the solid state. Our
attempts to engineer polar chains in mixed metal oxide fluorides M′(2,2′-bpy)(H<sub>2</sub>O)<sub>2</sub>MO<sub><i>x</i></sub>F<sub>6–<i>x</i></sub> compounds [M′/M = Cu/Ti, Cu/V, Cu/Nb, Cu/Mo,
Zn/Mo, and Zn/W] were successful using a combination of acentric anions
[MO<sub><i>x</i></sub>F<sub>6–<i>x</i></sub>]<sup>2–</sup> and acentric cations [M′(2,2′-bpy)(H<sub>2</sub>O)<sub>2</sub>]<sup>2+</sup>. A new general insight is also
revealed: the alignment of polar units can be described with a “lock
and key” model. The role of both the key (the acentric unit)
and the lock (its environment) on the polarity in infinite chains
is discussed
Alignment of Acentric Units in Infinite Chains: A “Lock and Key” Model
Polar
chains built from acentric building units are of importance to investigate
the mechanisms driving the polar alignment in the solid state. Our
attempts to engineer polar chains in mixed metal oxide fluorides M′(2,2′-bpy)(H<sub>2</sub>O)<sub>2</sub>MO<sub><i>x</i></sub>F<sub>6–<i>x</i></sub> compounds [M′/M = Cu/Ti, Cu/V, Cu/Nb, Cu/Mo,
Zn/Mo, and Zn/W] were successful using a combination of acentric anions
[MO<sub><i>x</i></sub>F<sub>6–<i>x</i></sub>]<sup>2–</sup> and acentric cations [M′(2,2′-bpy)(H<sub>2</sub>O)<sub>2</sub>]<sup>2+</sup>. A new general insight is also
revealed: the alignment of polar units can be described with a “lock
and key” model. The role of both the key (the acentric unit)
and the lock (its environment) on the polarity in infinite chains
is discussed
Alignment of Acentric Units in Infinite Chains: A “Lock and Key” Model
Polar
chains built from acentric building units are of importance to investigate
the mechanisms driving the polar alignment in the solid state. Our
attempts to engineer polar chains in mixed metal oxide fluorides M′(2,2′-bpy)(H<sub>2</sub>O)<sub>2</sub>MO<sub><i>x</i></sub>F<sub>6–<i>x</i></sub> compounds [M′/M = Cu/Ti, Cu/V, Cu/Nb, Cu/Mo,
Zn/Mo, and Zn/W] were successful using a combination of acentric anions
[MO<sub><i>x</i></sub>F<sub>6–<i>x</i></sub>]<sup>2–</sup> and acentric cations [M′(2,2′-bpy)(H<sub>2</sub>O)<sub>2</sub>]<sup>2+</sup>. A new general insight is also
revealed: the alignment of polar units can be described with a “lock
and key” model. The role of both the key (the acentric unit)
and the lock (its environment) on the polarity in infinite chains
is discussed
Assisting the Effective Design of Polar Iodates with Early Transition-Metal Oxide Fluoride Anions
Polar
materials are of great technical interest but challenging
to effectively synthesize. That is especially true for iodates, an
important class of visible and mid-IR transparent nonlinear optical
(NLO) materials. Aiming at developing a new design strategy for polar
iodates, we successfully synthesized two sets of polymorphic early
transition-metal (ETM) oxide-fluoride iodates, α- and β-Ba[VFO<sub>2</sub>(IO<sub>3</sub>)<sub>2</sub>] and α- and β-Ba<sub>2</sub>[VO<sub>2</sub>F<sub>2</sub>(IO<sub>3</sub>)<sub>2</sub>]IO<sub>3</sub>, based on the distinct structure-directing properties of
oxide-fluoride anions. α- and β-Ba[VFO<sub>2</sub>(IO<sub>3</sub>)<sub>2</sub>] contain the <i>trans</i>-[VFO<sub>2</sub>(IO<sub>3</sub>)<sub>2</sub>]<sup>2–</sup> polyanion
and crystallize in the nonpolar space groups <i>Pbcn</i> and <i>P</i>2<sub>1</sub>2<sub>1</sub>2<sub>1</sub>. In
contrast, α- and β-Ba<sub>2</sub>[VO<sub>2</sub>F<sub>2</sub>(IO<sub>3</sub>)<sub>2</sub>]IO<sub>3</sub> contain the <i>cis</i>-[VO<sub>2</sub>F<sub>2</sub>(IO<sub>3</sub>)<sub>2</sub>]<sup>3–</sup> Λ-shaped polyanion and crystallize in
the polar space groups <i>Pna</i>2<sub>1</sub> and <i>P</i>2<sub>1</sub>, respectively. Detailed structural analyses
show that the variable polar orientation of <i>trans</i>-[VFO<sub>2</sub>(IO<sub>3</sub>)<sub>2</sub>]<sup>2–</sup> polyanions is the main cause of the nonpolar structures in α-
and β-Ba[VFO<sub>2</sub>(IO<sub>3</sub>)<sub>2</sub>]. However,
the Λ-shaped configuration of <i>cis</i>-[VO<sub>2</sub>F<sub>2</sub>(IO<sub>3</sub>)<sub>2</sub>]<sup>3–</sup> polyanions
can effectively guarantee the polar structures. Further property measurements
show that polar α- and β-Ba<sub>2</sub>[VO<sub>2</sub>F<sub>2</sub>(IO<sub>3</sub>)<sub>2</sub>]IO<sub>3</sub> possess
excellent NLO properties, including the large SHG responses (∼9
× KDP), wide visible and mid-IR transparent region (∼0.5–10.5
μm), and high thermal stability (up to 470 °C). Therefore,
combining <i>cis</i>-directing oxide-fluoride anions and
iodates is a viable strategy for the effective design of polar iodates
From Racemic Units to Polar Materials
A new route is described
that enables the design of polar materials
using racemic basic building units (BBUs). Λ- and Δ-[Cu(H<sub>2</sub>O)(bpy)<sub>2</sub>]<sup>2+</sup> complexes in noncentrosymmetric
[Cu(H<sub>2</sub>O)(bpy)<sub>2</sub>]<sub>2</sub>[HfF<sub>6</sub>]<sub>2</sub>·3H<sub>2</sub>O and centrosymmetric [Cu(H<sub>2</sub>O)(bpy)<sub>2</sub>][BF<sub>4</sub>]<sub>2</sub> reveal that racemic
BBUs in the solid state can lead directly to noncentrosymmetry. The
structure is polar if only mirror or glide planes relate the left-
and right-handed enantiomers, whereas nonpolar, achiral structures
result if rotoinversion relates the left- and right-handed enantiomers.
This structural analysis also provides an alternative route in the
design of polar materials that had always been engineered from polar
BBUs
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