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)­(H₂O)₂MO_<i>x</i>F_6–<i>x</i> 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_<i>x</i>F_6–<i>x</i>]^2– and acentric cations [M′(2,2′-bpy)­(H₂O)₂]²⁺. 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)₂(H₂O)₂]­(ZrF₆)·3H₂O (<b>I</b>) and [Ni­(2,2′-bpy)₃]­(MoO₂F₄)·5H₂O (<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)­(H₂O)₂MO_<i>x</i>F_6–<i>x</i> 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_<i>x</i>F_6–<i>x</i>]^2– and acentric cations [M′(2,2′-bpy)­(H₂O)₂]²⁺. 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)­(H₂O)₂MO_<i>x</i>F_6–<i>x</i> 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_<i>x</i>F_6–<i>x</i>]^2– and acentric cations [M′(2,2′-bpy)­(H₂O)₂]²⁺. 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)₂(H₂O)₂]­(ZrF₆)·3H₂O (<b>I</b>) and [Ni­(2,2′-bpy)₃]­(MoO₂F₄)·5H₂O (<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)­(H₂O)₂MO_<i>x</i>F_6–<i>x</i> 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_<i>x</i>F_6–<i>x</i>]^2– and acentric cations [M′(2,2′-bpy)­(H₂O)₂]²⁺. 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)­(H₂O)₂MO_<i>x</i>F_6–<i>x</i> 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_<i>x</i>F_6–<i>x</i>]^2– and acentric cations [M′(2,2′-bpy)­(H₂O)₂]²⁺. 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)­(H₂O)₂MO_<i>x</i>F_6–<i>x</i> 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_<i>x</i>F_6–<i>x</i>]^2– and acentric cations [M′(2,2′-bpy)­(H₂O)₂]²⁺. 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[VFO₂(IO₃)₂] and α- and β-Ba₂[VO₂F₂(IO₃)₂]­IO₃, based on the distinct structure-directing properties of oxide-fluoride anions. α- and β-Ba­[VFO₂(IO₃)₂] contain the <i>trans</i>-[VFO₂(IO₃)₂]^2– polyanion and crystallize in the nonpolar space groups <i>Pbcn</i> and <i>P</i>2₁2₁2₁. In contrast, α- and β-Ba₂[VO₂F₂(IO₃)₂]­IO₃ contain the <i>cis</i>-[VO₂F₂(IO₃)₂]^3– Λ-shaped polyanion and crystallize in the polar space groups <i>Pna</i>2₁ and <i>P</i>2₁, respectively. Detailed structural analyses show that the variable polar orientation of <i>trans</i>-[VFO₂(IO₃)₂]^2– polyanions is the main cause of the nonpolar structures in α- and β-Ba­[VFO₂(IO₃)₂]. However, the Λ-shaped configuration of <i>cis</i>-[VO₂F₂(IO₃)₂]^3– polyanions can effectively guarantee the polar structures. Further property measurements show that polar α- and β-Ba₂[VO₂F₂(IO₃)₂]­IO₃ 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(H₂O)­(bpy)₂]²⁺ complexes in noncentrosymmetric [Cu­(H₂O)­(bpy)₂]₂[HfF₆]₂·3H₂O and centrosymmetric [Cu­(H₂O)­(bpy)₂]­[BF₄]₂ 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