Violation of Electrostatic Rules: Shifting Balance Between Pnicogen Bond and Lone Pair−π Interaction Tuned by Substituents

Complexes were formed pairing ZCl3 (Z=P, As, Sb) with C2R4 (R= H, F, CN). The first interaction present is a pnicogen bond between the Z atom and the C=C π-bond. This bond weakens as the H atoms of ethylene are replaced by electron-withdrawing F and CN and the potential above the alkene switches from negative to positive. In the latter two cases, another set of noncovalent bonds is formed between the Cl lone pairs of ZCl3 and the π*(C=C) antibonding orbital, as well as with the F or CN substituents. The growing strength of these interactions, coupled with a large dispersion energy, more than compensates for the weak pnicogen bond in C2(CN)4, with its repulsion between areas of positive charge on each subunit, making its complexes with ZCl3 very strong, as high as 25 kJ/mol. The pnicogen bond in C2F4 is weaker than in C2H4, and its subsidiary lone pair-π bonds weaker than in C2(CN)4, so the complexes of this alkene with ZCl3 are the weakest of the set

Creative Agents: Empowering Agents with Imagination for Creative Tasks

We study building embodied agents for open-ended creative tasks. While existing methods build instruction-following agents that can perform diverse open-ended tasks, none of them demonstrates creativity -- the ability to give novel and diverse task solutions implicit in the language instructions. This limitation comes from their inability to convert abstract language instructions into concrete task goals in the environment and perform long-horizon planning for such complicated goals. Given the observation that humans perform creative tasks with the help of imagination, we propose a class of solutions for creative agents, where the controller is enhanced with an imaginator that generates detailed imaginations of task outcomes conditioned on language instructions. We introduce several approaches to implementing the components of creative agents. We implement the imaginator with either a large language model for textual imagination or a diffusion model for visual imagination. The controller can either be a behavior-cloning policy learned from data or a pre-trained foundation model generating executable codes in the environment. We benchmark creative tasks with the challenging open-world game Minecraft, where the agents are asked to create diverse buildings given free-form language instructions. In addition, we propose novel evaluation metrics for open-ended creative tasks utilizing GPT-4V, which holds many advantages over existing metrics. We perform a detailed experimental analysis of creative agents, showing that creative agents are the first AI agents accomplishing diverse building creation in the survival mode of Minecraft. Our benchmark and models are open-source for future research on creative agents (https://github.com/PKU-RL/Creative-Agents).Comment: The first two authors contribute equall

Carbene Triel Bonds Between TrR3 (Tr=B, Al) and N-Heterocyclic Carbenes

The carbene triel bond is predicted and characterized by theoretical calculations. The C lone pair of N‐heterocyclic carbenes (NHCs) is allowed to interact with the central triel atom of TrR3 (Tr = B and Al; R = H, F, Cl, and Br). The ensuing bond is very strong, with an interaction energy of nearly 90 kcal/mol. Replacement of the C lone pair by that of either N or Si weakens the binding. The bond is strengthened by electron‐withdrawing substituents on the triel atom, and the reverse occurs with substitution on the NHC. However, these effects do not strictly follow the typical pattern of F \u3e Cl \u3e Br. The TrR3 molecule suffers a good deal of geometric deformation, requiring on the order of 30 kcal/mol, in forming the complex. The R(C···Tr) bond is quite short, for example, 1.6 Å for Tr = B, and shows other indications of at least a partially covalent bond, such as a high electron density at the bond critical point and a good deal of intermolecular charge transfer

Effect of Carbon Hybridization in C—F Bond as an Electron Donor in Triel Bonds

The ability of the F atom of HC≡CF, H2C=CHF and H3CCH2F to serve as an electron donor to the triel (Tr) atom of TrR3 in the context of a triel bond is assessed by ab initio calculations. The triel bond formed by Csp3—F is strongest, as high as 30 kcal/mol, followed by Csp2—F, and then by Csp—F whose triel bonds can be as small as 1 kcal/mol. The noncovalent bond strength diminishes in the order Tr = Al \u3e Ga \u3e B, consistent with the intensity of the π-hole above the Tr atom in the monomer. The triel bond strength of the Al and Ga complexes increases along with the electronegativity of the R substituent but is largest for R=H when Tr=B. Electrostatics play the largest role in the stronger triel bonds, but dispersion makes an outsized contribution for the weakest such bonds

Plan4MC: Skill Reinforcement Learning and Planning for Open-World Minecraft Tasks

We study building a multi-task agent in Minecraft. Without human demonstrations, solving long-horizon tasks in this open-ended environment with reinforcement learning (RL) is extremely sample inefficient. To tackle the challenge, we decompose solving Minecraft tasks into learning basic skills and planning over the skills. We propose three types of fine-grained basic skills in Minecraft, and use RL with intrinsic rewards to accomplish basic skills with high success rates. For skill planning, we use Large Language Models to find the relationships between skills and build a skill graph in advance. When the agent is solving a task, our skill search algorithm walks on the skill graph and generates the proper skill plans for the agent. In experiments, our method accomplishes 24 diverse Minecraft tasks, where many tasks require sequentially executing for more than 10 skills. Our method outperforms baselines in most tasks by a large margin. The project's website and code can be found at https://sites.google.com/view/plan4mc.Comment: 19 page