Herein, we describe the preparation of binary cocrystals and ternary and quaternary solid solutions of 1,4-diazabicyclo-[2.2.2]octane (DABCO) and 4-X-phenols (X = Cl, CH 3 , Br). Multicomponent solids, be they cocrystals or solid solutions, are materials that may exhibit new or superior functionalities relative to the individual components.[1] Though molecular complexes have been studied for a long time, [1][2][3] the design of cocrystals containing more than two different components remains a challenging task.[4] Except for a few notable contributions, [5] most studies on organic cocrystals led only to the formation of binary organic solids.[1] In contrast, metals and inorganic compounds readily form multicomponent solids in the form of solid solutions.[6] Creating multicomponent solid solutions of organic molecules, however, is challenging because these molecules possess intricate shapes and participate in directional intermolecular interactions. [3] Not surprisingly, most molecule-based solid solutions contain only two components. [7] We describe a supramolecular approach for the preparation of solid solutions that contain three or more organic molecules. The principal advantage of solid solutions is that their properties can be modulated by the gradual modification of the relative ratio of the components.[8]Scheme 1 shows our approach to the formation of organic alloys. We begin with a trimolecular motif wherein a central molecule (A) is connected to two peripheral molecules (B or C) through similar intermolecular interactions. If the two peripheral molecules are identical, the binary cocrystals AB 2 or AC 2 are formed. If they are different, a ternary cocrystal BAC or a ternary solid solution A(B n C 1Àn ) 2 (0 < n < 1) can be formed, depending on the similarity of the sizes and shapes of the peripheral molecules. Adding another isosteric component (D) can lead to a quaternary solid solution A(B n C m D p ) 2 (n + m + p = 1, 0 < n, m, p < 1).We use DABCO as the central molecule and 4-X-phenols (X = Cl, CH 3 , Br) as the peripheral molecules (Scheme 2). The chloro, methyl, and bromo substituents of the 4-Xphenols have similar shapes and comparable sizes (20, 24, and 28 3 ), [9] and do not interfere with the O À H···N hydrogen bonding required for the trimolecular assembly. We surmised that the size, shape, and chemical similarity of the 4-Xphenols would enable the formation of solid solutions upon crystallization of DABCO with two or three of the phenols. We call these crystalline materials supramolecular solid solutions because their repeat unit is a trimolecular assembly.[10]Single crystals of binary cocrystals and of ternary and quaternary solid solutions (having equimolar ratios of phenols) suitable for X-ray diffraction were grown from benzene solutions (Table 1; Scheme 2).[11] The binary cocrystals ClCl and MeMe are isostructural; [12] Figure 1 a shows the structure of ClCl. The unit cell of MeMe is larger than that of ClCl, in accordance with the larger size of the methyl groups relative to the chlo...

Herein, we describe the preparation of binary cocrystals and ternary and quaternary solid solutions of 1,4-diazabicyclo-[2.2.2]octane (DABCO) and 4-X-phenols (X = Cl, CH 3 , Br). Multicomponent solids, be they cocrystals or solid solutions, are materials that may exhibit new or superior functionalities relative to the individual components.[1] Though molecular complexes have been studied for a long time, [1][2][3] the design of cocrystals containing more than two different components remains a challenging task.[4] Except for a few notable contributions, [5] most studies on organic cocrystals led only to the formation of binary organic solids.[1] In contrast, metals and inorganic compounds readily form multicomponent solids in the form of solid solutions.[6] Creating multicomponent solid solutions of organic molecules, however, is challenging because these molecules possess intricate shapes and participate in directional intermolecular interactions. [3] Not surprisingly, most molecule-based solid solutions contain only two components. [7] We describe a supramolecular approach for the preparation of solid solutions that contain three or more organic molecules. The principal advantage of solid solutions is that their properties can be modulated by the gradual modification of the relative ratio of the components.[8]Scheme 1 shows our approach to the formation of organic alloys. We begin with a trimolecular motif wherein a central molecule (A) is connected to two peripheral molecules (B or C) through similar intermolecular interactions. If the two peripheral molecules are identical, the binary cocrystals AB 2 or AC 2 are formed. If they are different, a ternary cocrystal BAC or a ternary solid solution A(B n C 1Àn ) 2 (0 < n < 1) can be formed, depending on the similarity of the sizes and shapes of the peripheral molecules. Adding another isosteric component (D) can lead to a quaternary solid solution A(B n C m D p ) 2 (n + m + p = 1, 0 < n, m, p < 1).We use DABCO as the central molecule and 4-X-phenols (X = Cl, CH 3 , Br) as the peripheral molecules (Scheme 2). The chloro, methyl, and bromo substituents of the 4-Xphenols have similar shapes and comparable sizes (20, 24, and 28 3 ), [9] and do not interfere with the O À H···N hydrogen bonding required for the trimolecular assembly. We surmised that the size, shape, and chemical similarity of the 4-Xphenols would enable the formation of solid solutions upon crystallization of DABCO with two or three of the phenols. We call these crystalline materials supramolecular solid solutions because their repeat unit is a trimolecular assembly.[10]Single crystals of binary cocrystals and of ternary and quaternary solid solutions (having equimolar ratios of phenols) suitable for X-ray diffraction were grown from benzene solutions (Table 1; Scheme 2).[11] The binary cocrystals ClCl and MeMe are isostructural; [12] Figure 1 a shows the structure of ClCl. The unit cell of MeMe is larger than that of ClCl, in accordance with the larger size of the methyl groups relative to the chlo...

Organic alloys can be prepared by crystallizing 1,4-diazabicyclo[2.2.2]octane (DABCO) in the presence of up to three different 4-substituted phenols, as described by V. R. Thalladi et al. in their Communication on page 4132 ff. The repeat unit of these solids is a trimolecular assembly: a central DABCO molecule connected to two peripheral phenol molecules (see structure). Substitution of the different phenols with one another leads to ternary and quaternary solid solutions.

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